Apply clang-tidy fixes for llvm-qualified-auto in InterfaceAttachmentTest.cpp (NFC)

mlir/unittests/IR/InterfaceAttachmentTest.cpp

diff --git a/mlir/unittests/IR/InterfaceAttachmentTest.cpp b/mlir/unittests/IR/InterfaceAttachmentTest.cpp
index 2e1309a..16de34c 100644
--- a/mlir/unittests/IR/InterfaceAttachmentTest.cpp
+++ b/mlir/unittests/IR/InterfaceAttachmentTest.cpp
@@ -421,7 +421,7 @@
   // Attribute interfaces use the exact same mechanism as types, so just check
   // that the promise mechanism works for attributes.
   MLIRContext context;
-  auto testDialect = context.getOrLoadDialect<test::TestDialect>();
+  auto *testDialect = context.getOrLoadDialect<test::TestDialect>();
   auto attr = test::SimpleAAttr::get(&context);
 
   // `SimpleAAttr` doesn't implement nor promises the