layers: Remove DRAWSTATE_INVALID_POOL check

This check was only flagged when Allocating descriptor sets or resetting
a descriptor pool, and in both cases object_tracker will be the first layer
to identify and flag the error.

Removing this as a redundant check and updating documentation.
diff --git a/layers/descriptor_sets.cpp b/layers/descriptor_sets.cpp
index 10463ab..fa67b2c 100644
--- a/layers/descriptor_sets.cpp
+++ b/layers/descriptor_sets.cpp
@@ -1304,34 +1304,26 @@
         }
     }
     auto pool_node = getPoolNode(dev_data, p_alloc_info->descriptorPool);
-    if (!pool_node) {
-        skip_call |=
-            log_msg(report_data, VK_DEBUG_REPORT_ERROR_BIT_EXT, VK_DEBUG_REPORT_OBJECT_TYPE_DESCRIPTOR_POOL_EXT,
-                    reinterpret_cast<const uint64_t &>(p_alloc_info->descriptorPool), __LINE__, DRAWSTATE_INVALID_POOL, "DS",
-                    "Unable to find pool node for pool 0x%" PRIxLEAST64 " specified in vkAllocateDescriptorSets() call",
-                    reinterpret_cast<const uint64_t &>(p_alloc_info->descriptorPool));
-    } else { // Make sure pool has all the available descriptors before calling down chain
-        // Track number of descriptorSets allowable in this pool
-        if (pool_node->availableSets < p_alloc_info->descriptorSetCount) {
-            skip_call |=
-                log_msg(report_data, VK_DEBUG_REPORT_ERROR_BIT_EXT, VK_DEBUG_REPORT_OBJECT_TYPE_DESCRIPTOR_POOL_EXT,
-                        reinterpret_cast<uint64_t &>(pool_node->pool), __LINE__, DRAWSTATE_DESCRIPTOR_POOL_EMPTY, "DS",
-                        "Unable to allocate %u descriptorSets from pool 0x%" PRIxLEAST64
-                        ". This pool only has %d descriptorSets remaining.",
-                        p_alloc_info->descriptorSetCount, reinterpret_cast<uint64_t &>(pool_node->pool), pool_node->availableSets);
-        }
-        // Determine whether descriptor counts are satisfiable
-        for (uint32_t i = 0; i < VK_DESCRIPTOR_TYPE_RANGE_SIZE; i++) {
-            if (ds_data->required_descriptors_by_type[i] > pool_node->availableDescriptorTypeCount[i]) {
-                skip_call |= log_msg(report_data, VK_DEBUG_REPORT_ERROR_BIT_EXT, VK_DEBUG_REPORT_OBJECT_TYPE_DESCRIPTOR_POOL_EXT,
-                                     reinterpret_cast<const uint64_t &>(pool_node->pool), __LINE__, DRAWSTATE_DESCRIPTOR_POOL_EMPTY,
-                                     "DS", "Unable to allocate %u descriptors of type %s from pool 0x%" PRIxLEAST64
-                                           ". This pool only has %d descriptors of this type remaining.",
-                                     ds_data->required_descriptors_by_type[i], string_VkDescriptorType(VkDescriptorType(i)),
-                                     reinterpret_cast<uint64_t &>(pool_node->pool), pool_node->availableDescriptorTypeCount[i]);
-            }
+    // Track number of descriptorSets allowable in this pool
+    if (pool_node->availableSets < p_alloc_info->descriptorSetCount) {
+        skip_call |= log_msg(
+            report_data, VK_DEBUG_REPORT_ERROR_BIT_EXT, VK_DEBUG_REPORT_OBJECT_TYPE_DESCRIPTOR_POOL_EXT,
+            reinterpret_cast<uint64_t &>(pool_node->pool), __LINE__, DRAWSTATE_DESCRIPTOR_POOL_EMPTY, "DS",
+            "Unable to allocate %u descriptorSets from pool 0x%" PRIxLEAST64 ". This pool only has %d descriptorSets remaining.",
+            p_alloc_info->descriptorSetCount, reinterpret_cast<uint64_t &>(pool_node->pool), pool_node->availableSets);
+    }
+    // Determine whether descriptor counts are satisfiable
+    for (uint32_t i = 0; i < VK_DESCRIPTOR_TYPE_RANGE_SIZE; i++) {
+        if (ds_data->required_descriptors_by_type[i] > pool_node->availableDescriptorTypeCount[i]) {
+            skip_call |= log_msg(report_data, VK_DEBUG_REPORT_ERROR_BIT_EXT, VK_DEBUG_REPORT_OBJECT_TYPE_DESCRIPTOR_POOL_EXT,
+                                 reinterpret_cast<const uint64_t &>(pool_node->pool), __LINE__, DRAWSTATE_DESCRIPTOR_POOL_EMPTY,
+                                 "DS", "Unable to allocate %u descriptors of type %s from pool 0x%" PRIxLEAST64
+                                       ". This pool only has %d descriptors of this type remaining.",
+                                 ds_data->required_descriptors_by_type[i], string_VkDescriptorType(VkDescriptorType(i)),
+                                 reinterpret_cast<uint64_t &>(pool_node->pool), pool_node->availableDescriptorTypeCount[i]);
         }
     }
+
     return skip_call;
 }
 // Decrement allocated sets from the pool and insert new sets into set_map