FindRuby: Remove documentation for non-existent Ruby_ROOT_DIR
Documentation was added by !4386 (merged), but this feature was never implemented.
Closes: #21528 (closed)
Backport: release
Topic-rename: FindRuby-doc-fix
Edited by Brad King
Documentation was added by !4386 (merged), but this feature was never implemented.
Closes: #21528 (closed)
Backport: release
Topic-rename: FindRuby-doc-fix