fix(rhc): bug in replica-healthcheck dockerfile

Fixes a bug in the dockerfile for the replica-healthcheck. Healthcheck
does not run properly as a result of this bug.

.changeset/healthy-rings-fix.md

+---
+'@eth-optimism/replica-healthcheck': patch
+---
+
+Fixes a bug in the replica-healthcheck dockerfile

ops/docker/Dockerfile.packages

@@ -62,4 +62,4 @@ CMD ["npm", "run", "start"]
 
 FROM base as replica-healthcheck
 WORKDIR /opts/optimism/packages/replica-healthcheck
-ENTRYPOINT ["node", "dist/exec/run-healthcheck-server.js"]
+ENTRYPOINT ["npm", "run", "start"]