init: silence zcompdump metadata write for invalid ZSH_COMPDUMP filenames

If `$SHORT_HOST` contains invalid filename characters, the compinit call doesn't
error, but the zcompdump metadata write does. Use `tee` instead so we can silence
the error.

See https://github.com/ohmyzsh/ohmyzsh/commit/dd1a72696f162fd5285a104b5f63970deb66e8b0#commitcomment-38984764

oh-my-zsh.sh

@@ -86,7 +86,7 @@ fi
 
 # Append zcompdump metadata if missing
 if (( $zcompdump_refresh )); then
-  echo "\n$zcompdump_metadata" >>! "$ZSH_COMPDUMP"
+  echo "\n$zcompdump_metadata" | tee -a "$ZSH_COMPDUMP" &>/dev/null
 fi
 
 unset zcompdump_metadata zcompdump_refresh