[mlir] Rename StringRef _lower() method calls to _insensitive()

Author: mstorsjo

mlir/test/lib/Dialect/Test/TestTypes.cpp

@@ -31,11 +31,14 @@ parseSignedness(DialectAsmParser &parser,
   auto loc = parser.getCurrentLocation();
   if (parser.parseKeyword(&signStr))
     return failure();
-  if (signStr.compare_lower("u") || signStr.compare_lower("unsigned"))
+  if (signStr.compare_insensitive("u") ||
+      signStr.compare_insensitive("unsigned"))
     result = TestIntegerType::SignednessSemantics::Unsigned;
-  else if (signStr.compare_lower("s") || signStr.compare_lower("signed"))
+  else if (signStr.compare_insensitive("s") ||
+           signStr.compare_insensitive("signed"))
     result = TestIntegerType::SignednessSemantics::Signed;
-  else if (signStr.compare_lower("n") || signStr.compare_lower("none"))
+  else if (signStr.compare_insensitive("n") ||
+           signStr.compare_insensitive("none"))
     result = TestIntegerType::SignednessSemantics::Signless;
   else
     return parser.emitError(loc, "expected signed, unsigned, or none");