Use common strings in spotify config flow (#40957)

homeassistant/components/spotify/strings.json

 {
   "config": {
     "step": {
-      "pick_implementation": { "title": "[%key:common::config_flow::title::oauth2_pick_implementation%]" },
+      "pick_implementation": {
+        "title": "[%key:common::config_flow::title::oauth2_pick_implementation%]"
+      },
       "reauth_confirm": {
         "title": "Re-authenticate with Spotify",
         "description": "The Spotify integration needs to re-authenticate with Spotify for account: {account}"
       }
     },
     "abort": {
-      "already_setup": "You can only configure one Spotify account.",
       "authorize_url_timeout": "Timeout generating authorize url.",
       "no_url_available": "[%key:common::config_flow::abort::oauth2_no_url_available%]",
       "missing_configuration": "The Spotify integration is not configured. Please follow the documentation.",