[test] Mark print_clang_header_swift_name.swift as requiring ObjC.

Enums with fixed underlying type are a C++ and Objective-C feature,
but are not available in C, even as a Clang extension.

Author: jrose-apple

test/IDE/print_clang_header_swift_name.swift

@@ -3,6 +3,8 @@
 // RUN:     %S/Inputs/print_clang_header_swift_name.h --cc-args %target-cc-options \
 // RUN:     -isysroot %clang-importer-sdk-path -fsyntax-only %t.m -I %S/Inputs | FileCheck %s
 
+// REQUIRES: objc_interop
+
 // CHECK: enum Normal : Int {
 // CHECK-NOT: {{^}}}
 // CHECK: case One