chore(deps): update ghcr.io/open-feature/sync-testbed-unstable docker tag to v0.5.3 (#746)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

Diff for: .github/workflows/ci.yml

@@ -29,7 +29,7 @@ jobs:
           - 9090:9090
       # sync-testbed for flagd in-process provider reconnect e2e tests
       sync-unstable:
-        image: ghcr.io/open-feature/sync-testbed-unstable:v0.5.2
+        image: ghcr.io/open-feature/sync-testbed-unstable:v0.5.3
         ports:
           - 9091:9090