overlayworkingctx: remove misleading trailing slash from directory pattern The paths passed into the matcher are normalized (this applies to include patterns and regular patterns, and to both glob kind and path kind), so the regex for input "foo/" ended up being "foo(?:/|$)". Once we have a (recursive) pattern kind only for directories, we could switch to that here and remove the "mfiles[0] == path" check. Until then, let's at least make it not misleading. Differential Revision: https://phab.mercurial-scm.org/D6224