remove .verification_codes.json (real emails in cleartext)

File contained signup verification codes mapped to real Gmail addresses
(maxon@gmail.com, samuelbanky2007@gmail.com) plus a stream of test
addresses. The codes are expired, but the emails are real personal
data and should never have been committed.

Added to .gitignore. About to be scrubbed from full git history in the
next operation.

Author: Octopoda Release

.gitignore

@@ -113,3 +113,4 @@ scripts/create_admin_activation_fn.py
 scripts/test_free_tier_cap.py
 scripts/test_stripe_full_sequence.py
 scripts/test_tenant_isolation.py
+.verification_codes.json