BitcodeWriter: Replace dead code with an assertion, NFC

The caller of ValueEnumerator::EnumerateOperandType never sends in
metadata.  Assert that, and remove the unnecessary logic.

llvm-svn: 264558
diff --git a/llvm/lib/Bitcode/Writer/ValueEnumerator.cpp b/llvm/lib/Bitcode/Writer/ValueEnumerator.cpp
index 812baf2..4e0a9da 100644
--- a/llvm/lib/Bitcode/Writer/ValueEnumerator.cpp
+++ b/llvm/lib/Bitcode/Writer/ValueEnumerator.cpp
@@ -660,13 +660,7 @@
 void ValueEnumerator::EnumerateOperandType(const Value *V) {
   EnumerateType(V->getType());
 
-  if (auto *MD = dyn_cast<MetadataAsValue>(V)) {
-    assert(!isa<LocalAsMetadata>(MD->getMetadata()) &&
-           "Function-local metadata should be left for later");
-
-    EnumerateMetadata(MD->getMetadata());
-    return;
-  }
+  assert(!isa<MetadataAsValue>(V) && "Unexpected metadata operand");
 
   const Constant *C = dyn_cast<Constant>(V);
   if (!C)