[keyserver] Fix synchronizing invite links with blobs

Summary:
We were encoding the hashes twice - once in this method and again in uploadInviteLinkBlob.

https://linear.app/comm/issue/ENG-9715/blobs-with-invite-invite-prefix

Test Plan: Create a new invite link. Rename it by hand. Check the blob service - a blob for the modified link shouldn't exist. Force the script to run - the correct blob should appear.

Reviewers: kamil, angelika

Reviewed By: kamil

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D13767