community/bfs: upgrade to 2.6.1

According to fish documentation

The completions shipped with fish, usually installed in /usr/share/fish/completions

A directory for third-party software vendors to ship their own completions for their software, usually /usr/share/fish/vendor_completions.d

Although it doesn't hurt to place all completions under /usr/share/fish/completions, the abuild hook for splitting fish completions, by default, looks under /usr/share/fish/completions whereas bfs installs them under /usr/share/fish/vendor_completions.d, hence patch the Makefile is required.