Remove XFAIL on string view test for apples clang compiler. Thanks to Marshall for the fix

llvm-svn: 230322
diff --git a/libcxx/test/std/experimental/string.view/string.view.access/at.pass.cpp b/libcxx/test/std/experimental/string.view/string.view.access/at.pass.cpp
index 0030afa..3003ea8 100644
--- a/libcxx/test/std/experimental/string.view/string.view.access/at.pass.cpp
+++ b/libcxx/test/std/experimental/string.view/string.view.access/at.pass.cpp
@@ -9,7 +9,7 @@
 
 // NOTE: Older versions of clang have a bug where they fail to evalute
 // string_view::at as a constant expression.
-// XFAIL: apple-clang-6.0, clang-3.4, clang-3.3
+// XFAIL: clang-3.4, clang-3.3
 
 // <string_view>