git: add git rm aliases (#5433)

* grm for 'git rm'
* grmc for 'git rm --cached'

plugins/git/git.plugin.zsh

@@ -220,6 +220,8 @@ alias grbm='git rebase master'
 alias grbs='git rebase --skip'
 alias grh='git reset'
 alias grhh='git reset --hard'
+alias grm='git rm'
+alias grmc='git rm --cached'
 alias grmv='git remote rename'
 alias grrm='git remote remove'
 alias grset='git remote set-url'