[docs] Fix documentation for bugprone-dangling-handle

[malcolm.parsons]

Summary

string_view isn't experimental anymore.
This check has always handled both forms.

[aaron.ballman]

LGTM, thanks!

clang-tools-extra/docs/clang-tidy/checks/bugprone-dangling-handle.rst

 .. title:: clang-tidy - bugprone-dangling-handle
 
 bugprone-dangling-handle
 ========================
 
-Detect dangling references in value handles like
-``std::experimental::string_view``.
+Detect dangling references in value handles like ``std::string_view``.
 These dangling references can be a result of constructing handles from temporary
 values, where the temporary is destroyed soon after the handle is created.
 
 Examples:
 
 .. code-block:: c++
 
   string_view View = string();  // View will dangle.
.. code-block:: c++
   }
 
 Options
 -------
 
 .. option:: HandleClasses
 
    A semicolon-separated list of class names that should be treated as handles.
-   By default only ``std::experimental::basic_string_view`` is considered.
+   By default only ``std::basic_string_view`` and
+   ``std::experimental::basic_string_view`` are considered.