Fix this test to be more robust

The test is failing because it lacks a target triple, so the number of
diagnostics differs between Windows and Linux targets.

This should correct the issue found by:
https://lab.llvm.org/buildbot/#/builders/109/builds/46804

clang/test/CXX/drs/dr4xx.cpp

@@ -1013,7 +1013,7 @@ namespace dr483 { // dr483: yes
     int check4[__LONG_MAX__ >= 2147483647 ? 1 : -1];
     int check5[__LONG_LONG_MAX__ >= 9223372036854775807 ? 1 : -1];
 #if __cplusplus < 201103L
-    // expected-error@-2 2{{extension}}
+    // expected-error@-2 1+{{extension}}
 #endif
   }
   namespace cstdint {