chore(deps): update ghcr.io/open-feature/flagd-testbed-unstable docker tag to v0.5.20

Author: renovate[bot]

libs/providers/flagd/docker-compose.yaml

@@ -4,7 +4,7 @@ services:
     ports:
       - 8013:8013
   flagd-unstable:
-    image: ghcr.io/open-feature/flagd-testbed-unstable:v0.5.13
+    image: ghcr.io/open-feature/flagd-testbed-unstable:v0.5.20
     ports:
       - 8014:8013
   flagd-sync: