Revert "Suppress -Wctad-maybe-unsupported on types w/o deduction guides."

Some modules builds are issuing buggy diagnostics. The cause of which is
TBD.

This reverts commit r@367770.

llvm-svn: 367777
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 278d59301446afb40f0345bd411099fa311291a4
diff --git a/include/functional b/include/functional
index dd65f1b..865a281 100644
--- a/include/functional
+++ b/include/functional
@@ -3067,8 +3067,7 @@
     _ForwardIterator __first_;
     _ForwardIterator __last_;
     _BinaryPredicate __pred_;
-};
-_LIBCPP_CTAD_SUPPORTED_FOR_TYPE(default_searcher);
+    };
 
 #endif // _LIBCPP_STD_VER > 14