fix(ci): pin conformance test to formae 0.77.16-internal

Remove vars.FORMAE_VERSION indirection in favor of explicit version pinning.

Author: JeroenSoeters

.github/workflows/ci.yml

@@ -117,4 +117,4 @@ jobs:
         env:
           AWS_REGION: us-east-1
           FORMAE_TEST_RUN_ID: ${{ github.run_id }}-${{ github.run_attempt }}
-        run: make conformance-test VERSION=${{ vars.FORMAE_VERSION || '0.77.16-internal' }}
+        run: make conformance-test VERSION=0.77.16-internal