[split] Move chruby plugin to oh-my-fish/plugin-chruby

https://github.com/oh-my-fish/plugin-chruby

plugins/chruby/README.md

-## chruby plugin
-
-Depends on `chruby-fish`: https://github.com/JeanMertz/chruby-fish
-
-set `CHRUBY_AUTO_ENABLED` to `false` to disable auto loading Ruby versions on
-directory change.
-
-set `CHRUBY_ROOT` to point to the root path of chruby. The path will be
-appended by `share/chruby/chruby.fish` and `share/chruby/auto.fish`.

plugins/chruby/chruby.load

-#
-# Depends on `chruby-fish` (https://github.com/JeanMertz/chruby-fish)
-#
-# set `CHRUBY_AUTO_ENABLED` to `false` to disable auto loading Ruby versions on
-# directory change.
-#
-# set `CHRUBY_ROOT` to point to the root path of chruby. The path will be
-# appended by `share/chruby/chruby.fish` and `share/chruby/auto.fish`.
-#
-set -q CHRUBY_ROOT; or set CHRUBY_ROOT /usr/local
-
-if test -f "$CHRUBY_ROOT/share/chruby/chruby.fish"
-  . "$CHRUBY_ROOT/share/chruby/chruby.fish"
-else
-  echo '`chruby` plugin loaded but chruby-fish not installed.' \
-       'See: https://github.com/JeanMertz/chruby-fish'
-end
-
-if test "$CHRUBY_AUTO_ENABLED" != "false" -a \
-        -f "$CHRUBY_ROOT/share/chruby/auto.fish"
-
-  . "$CHRUBY_ROOT/share/chruby/auto.fish"
-end