Change title of section to reflect the concept, and not the mechanism.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@193277 91177308-0d34-0410-b5e6-96231b3b80d8

docs/LanguageExtensions.rst

@@ -1176,8 +1176,9 @@ of this feature in version of clang being used.
 
 .. _langext-objc_method_family:
 
-The ``objc_method_family`` attribute
-------------------------------------
+
+Objective-C Method Families
+---------------------------
 
 Many methods in Objective-C have conventional meanings determined by their
 selectors. It is sometimes useful to be able to mark a method as having a