zsh-completions: remove tmuxp completion

tmuxp now installs the completion so we need to remove this to avoid a
collision.

Signed-off-by: Otavio Salvador <[e-mail]>

pkgs/shells/zsh/zsh-completions/default.nix

···
   strictDeps = true;
   installPhase = ''
     install -D --target-directory=$out/share/zsh/site-functions src/*
+
+    # tmuxp install it so avoid collision
+    rm $out/share/zsh/site-functions/_tmuxp
   '';
 
   meta = {