Brewfile: install the latest CMake

Earlier we had trouble with CMake 3.20, and reverting to 3.16
worked around the problem. However this version is no longer
available in homebrew, so the `brew bundle` step is failing
in github ci. Try installing the latest version instead.

Currently that's CMake 3.22.1.

Brewfile

@@ -5,5 +5,5 @@ brew 'autoconf'
 brew 'automake'
 brew 'libtool'
 brew 'pkg-config'
-brew 'cmake@3.16'
+brew 'cmake'
 brew 'doxygen'