[mlir][NFC] Update textual references of `func` to `func.func` in Transform tests
The special case parsing of `func` operations is being removed.
diff --git a/mlir/test/Transforms/test-legalize-unknown-root.mlir b/mlir/test/Transforms/test-legalize-unknown-root.mlir
index c31840d..968d7e3 100644
--- a/mlir/test/Transforms/test-legalize-unknown-root.mlir
+++ b/mlir/test/Transforms/test-legalize-unknown-root.mlir
@@ -2,7 +2,7 @@
// Test that all `test` dialect operations are removed.
// CHECK-LABEL: func @remove_all_ops
-func @remove_all_ops(%arg0: i32) {
+func.func @remove_all_ops(%arg0: i32) {
// CHECK-NEXT: return
%0 = "test.illegal_op_a"() : () -> i32
%1 = "test.illegal_op_b"() : () -> i32
