ci: remove concurrency group entirely — V2 lakehouse naming already isolates all runs

Agent-Logs-Url: https://github.com/microsoft/dbt-fabricspark/sessions/6539a12a-b206-42f4-aa32-e017095a906b

Co-authored-by: mdrakiburrahman <46581776+mdrakiburrahman@users.noreply.github.com>

Author: Copilot

.github/workflows/ci.yml

@@ -4,10 +4,6 @@ on:
   pull_request:
   workflow_dispatch:
 
-concurrency:
-  group: ${{ github.workflow }}-${{ github.ref }}
-  cancel-in-progress: false
-
 env:
   IS_GH_ACTION: "1"
   CLIENT_ID: ${{ secrets.APP_ID }}