ci: pin sdk compliance harness 0.5.2

Author: marandaneto

.github/workflows/sdk-compliance.yml

@@ -14,8 +14,8 @@ on:
 jobs:
   compliance:
     name: PostHog SDK compliance tests
-    uses: PostHog/posthog-sdk-test-harness/.github/workflows/test-sdk-action.yml@39d05346c4638d24f94e591ab89c9c6fcdb52d6b
+    uses: PostHog/posthog-sdk-test-harness/.github/workflows/test-sdk-action.yml@v0.5.2
     with:
       adapter-dockerfile: "sdk_compliance_adapter/Dockerfile"
       adapter-context: "."
-      test-harness-version: "latest"
+      test-harness-version: "0.5.2"