Add keyserver/certs to .dockerignore

Summary: This makes sure we don't ever see something like [ENG-9181](https://linear.app/comm/issue/ENG-9181/remove-apn-p8-files-from-keyserver-docker-images) again.

Test Plan: N/A

Reviewers: will

Reviewed By: will

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D13369

.dockerignore

@@ -34,6 +34,7 @@ web/backup-client-wasm/target
 keyserver/dist
 keyserver/node_modules
 keyserver/facts
+keyserver/certs
 keyserver/secrets
 keyserver/*.env
 keyserver/*.env.*