Make base_nocompile_tests pass with recent Clang

Looks like the space between the two right angle brackets is gone with recent
Clang. The test expectation is already a regex, so insert a '?' to make the
space optional.

TBR=tzik

Bug: 1064986
Change-Id: I3075116ff2b344a5e13658cd2fd6b92522d58aeb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2124453Reviewed-by: Hans Wennborg <hans@chromium.org>
Commit-Queue: Hans Wennborg <hans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#754005}

base/bind_unittest.nc

@@ -268,7 +268,7 @@ void WontCompile() {
   std::move(cb).Run();
 }
 
-#elif defined(NCTEST_DISALLOW_BIND_ONCECALLBACK)  // [r"fatal error: static_assert failed due to requirement '!base::internal::IsOnceCallback<base::OnceCallback<void \(int\)> >\(\)' \"BindRepeating cannot bind OnceCallback. Use BindOnce with std::move\(\).\""]
+#elif defined(NCTEST_DISALLOW_BIND_ONCECALLBACK)  // [r"fatal error: static_assert failed due to requirement '!base::internal::IsOnceCallback<base::OnceCallback<void \(int\)> ?>\(\)' \"BindRepeating cannot bind OnceCallback. Use BindOnce with std::move\(\).\""]
 
 void WontCompile() {
   BindRepeating(BindOnce([](int) {}), 42);