ci: force test build-cache recreation to fix stale MP3 MAD NIF

The test job restored a `_build/test` cache whose MP3 MAD decoder NIF
(.so) was built against an older docker_membrane base image. After the
image was updated the cached NIF no longer loads, causing every pipeline
test that uses Membrane.MP3.MAD.Decoder to crash with
UndefinedFunctionError on ...Native.Nif.unifex_create/0. `mix compile
--force` only forces Elixir recompilation, not the cached bundlex NIF.

Bump the test workflow's cache-version so deps and the build cache are
recreated, rebuilding the NIF against the current image.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: FelonEkonom

.github/workflows/ci.yml

@@ -14,3 +14,10 @@ jobs:
 
   test:
     uses: membraneframework/membrane_actions/.github/workflows/test.yml@main
+    with:
+      # Bumped to force recreation of the stale test build cache: a previously
+      # cached MP3 MAD decoder NIF (.so) was built against an older
+      # docker_membrane base image and fails to load (UndefinedFunctionError on
+      # Membrane.MP3.MAD.Decoder.Native.Nif.unifex_create/0) after the image was
+      # updated. Forcing a fresh build rebuilds the NIF against the current image.
+      cache-version: 2