Keep single default PHP language server (#43432)

https://github.com/zed-extensions/php/blob/9a119b18eeb247072964a19ce46fab54bbd1bb30/extension.toml
provides 3 language servers for `php`, so `...` will always include all
3 if those are not excluded or included explicitly.

Change the configs and docs so, that only one php language server is
used.

Release Notes:

- N/A

docs/src/languages/php.md

@@ -35,7 +35,7 @@ To switch to `intelephense`, add the following to your `settings.json`:
 {
   "languages": {
     "PHP": {
-      "language_servers": ["intelephense", "!phpactor", "..."]
+      "language_servers": ["intelephense", "!phpactor", "!phptools", "..."]
     }
   }
 }