Revert "funced: Use variable-as-command"

This reverts commit 3253893923.

Fixes #5625.

share/functions/funced.fish

@@ -94,7 +94,7 @@ function funced --description 'Edit function definition'
     while true
         set -l checksum (__funced_md5 "$tmpname")
 
-        if not $editor $tmpname
+        if not eval $editor $tmpname
             echo (_ "Editing failed or was cancelled")
         else
             # Verify the checksum (if present) to detect potential problems