[keyserver] fix production check while uploading keys to Identity

Summary:
Fixing regression introduced in D9427.

This shouldn't affect anything, the only risk is that migration could make a silent fail on prod because the condition returns false always - but this is not what we want.

I discovered on my local setup that process.env.NODE_ENV === 'production' will not work because this env value is never set to production (this might be the fault of some missing .env files on my setup), but based on the code we only set NODE_ENV for dev, so changing this for safer solution.

Test Plan:

1. Terminate Identity
2. Test migration on prod (fail) / dev (only warning)

Reviewers: michal, marcin, ashoat

Reviewed By: ashoat

Subscribers: tomek, wyilio

Differential Revision: https://phab.comm.dev/D9505