[keyserver] Narrow updateRelationshipInputValidator to exclude farcaster action

Summary:
Modify updateRelationshipInputValidator so action is an enum of traditionalRelationshipActionsList vs relationshipActionsList.

Depends on D11609

Test Plan: Tried making request with farcaster action and it failed as expected.

Reviewers: ginsu, tomek, varun, will

Reviewed By: tomek

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D11610