Suppress clang-tidy error to use `auto` in tree_test.cpp (#3570)

toolchain/parse/tree_test.cpp

@@ -81,18 +81,23 @@ TEST_F(TreeTest, AsAndTryAs) {
   fn_decl_id = tree.TryAs<FunctionDeclId>(n);
   ASSERT_TRUE(fn_decl_id.has_value());
   EXPECT_TRUE(*fn_decl_id == n);
+  // Under normal usage, this function should be used with `auto`, but for
+  // a test it is nice to verify that it is returning the expected type.
+  // NOLINTNEXTLINE(modernize-use-auto).
   FunctionDeclId fn_decl_id2 = tree.As<FunctionDeclId>(n);
   EXPECT_TRUE(*fn_decl_id == fn_decl_id2);
 
   any_fn_decl_id = tree.TryAs<AnyFunctionDeclId>(n);
   ASSERT_TRUE(any_fn_decl_id.has_value());
   EXPECT_TRUE(*any_fn_decl_id == n);
+  // NOLINTNEXTLINE(modernize-use-auto).
   AnyFunctionDeclId any_fn_decl_id2 = tree.As<AnyFunctionDeclId>(n);
   EXPECT_TRUE(*any_fn_decl_id == any_fn_decl_id2);
 
   any_decl_id = tree.TryAs<AnyDeclId>(n);
   ASSERT_TRUE(any_decl_id.has_value());
   EXPECT_TRUE(*any_decl_id == n);
+  // NOLINTNEXTLINE(modernize-use-auto).
   AnyDeclId any_decl_id2 = tree.As<AnyDeclId>(n);
   EXPECT_TRUE(*any_decl_id == any_decl_id2);
 }