ci: add concurrency group to functions.yaml to cancel redundant runs

[Ankitsinghsisodya]

Problem

.github/workflows/functions.yaml has no concurrency configuration. When multiple commits are pushed to the same PR/branch in quick succession, multiple workflow runs execute simultaneously. This wastes CI minutes on stale runs that are no longer relevant.

Fix

Add a concurrency group to cancel in-progress runs when a new one starts:

concurrency:
  group: ${{ github.workflow }}-${{ github.ref }}
  cancel-in-progress: true

This ensures only the latest run for a given branch/PR is active at a time.

[Ankitsinghsisodya]

/assign