Fix documentation URL in AvoidBindCheck.h

[cbachhuber]

Summary

The URL on current master is a 404. This change fixes that and leads to the correct page.

clang-tools-extra/clang-tidy/modernize/AvoidBindCheck.h

 namespace tidy {
 namespace modernize {
 
 /// Replace simple uses of std::bind with a lambda.
 ///
 /// FIXME: Add support for function references and member function references.
 ///
 /// For the user-facing documentation see:
-/// http://clang.llvm.org/extra/clang-tidy/checks/modernize-avoid-std-bind.html
+/// http://clang.llvm.org/extra/clang-tidy/checks/modernize-avoid-bind.html
 class AvoidBindCheck : public ClangTidyCheck {
 public:
   AvoidBindCheck(StringRef Name, ClangTidyContext *Context);
   bool isLanguageVersionSupported(const LangOptions &LangOpts) const override {
     return LangOpts.CPlusPlus14;
   }
   void storeOptions(ClangTidyOptions::OptionMap &Opts) override;
   void registerMatchers(ast_matchers::MatchFinder *Finder) override;