Fix error in PrettyType.

PrettyType was incorrectly adding a space at the end of the type.

Also added a brief comment explaining what pretty type does.

Change-Id: Ia8b6f583a44d86a8c0db5efcd9ad495b686995d3
diff --git a/src/utils.cc b/src/utils.cc
index d038f6d..4efb177 100644
--- a/src/utils.cc
+++ b/src/utils.cc
@@ -279,10 +279,7 @@
 
 std::string PrettyType(uint32_t type_idx, const DexFile& dex_file) {
   const DexFile::TypeId& type_id = dex_file.GetTypeId(type_idx);
-  std::string result;
-  result += PrettyDescriptor(dex_file.GetTypeDescriptor(type_id));
-  result += ' ';
-  return result;
+  return PrettyDescriptor(dex_file.GetTypeDescriptor(type_id));
 }
 
 std::string PrettyArguments(const char* signature) {