Properly cleanup fresh prompt theme

If `prompt <theme>` is used, prior to this patch the `fresh_line_one`
precmd hook would not be removed. This is no longer the case and cleanup
is correctly performed.

prompt_fresh_setup

@@ -60,6 +60,12 @@ prompt_cleanup() {
 }
 
 fresh_line_one() {
+  # Clean up if fresh is no longer the current prompt theme
+  if [[ "`prompt -c | tail -1 | xargs`" != "fresh" ]]; then
+    add-zsh-hook -d precmd fresh_line_one
+    return
+  fi
+
   # First get the last commands exit code before doing anything
   local exit_code=$?