Update OWNERS for keymaster Java code

Since Janis has left, it makes no sense to have him on the OWNERS file.
Add myself as a reviewer in an EMEA-friendly timezone.

Test: N/A, owners change only.
BYPASS_INCLUSIVE_LANGUAGE_REASON=Janis used a he/him pronoun.

Change-Id: Ieab9ab74c1d11013ffa915999bf37773659cdad0