feat: update version in readme

Author: ablaszkiewicz

README.md

@@ -44,7 +44,7 @@ jobs:
 
       # Inject and upload source maps using this action
       - name: Inject & upload source maps to PostHog
-        uses: PostHog/upload-source-maps
+        uses: PostHog/upload-source-maps@v0.4.6
         with:
           directory: dist
           env-id: ${{ secrets.POSTHOG_ENV_ID }}