README: Drop outdated link on running CMake

README.rst

@@ -51,11 +51,8 @@ Building CMake with CMake
 -------------------------
 
 You can build CMake as any other project with a CMake-based build system:
-run the installed CMake on the sources of this CMake with your preferred
-options and generators. Then build it and install it.
-For instructions how to do this, see documentation on `Running CMake`_.
-
-.. _`Running CMake`: https://cmake.org/runningcmake
+run an already-installed CMake on this source tree with your preferred
+generator and options.  Then build it and install it.
 
 To build the documentation, install `Sphinx`_ and configure CMake with
 ``-DSPHINX_HTML=ON`` and/or ``-DSPHINX_MAN=ON`` to enable the "html" or