API to add admins from another SCM context fails when request has more than 50 users

[sagar1312]

What happened:
API /pipelines/updateAdmins accepts list of SCM usernames for a SCM context to be added as admins.
Schema limits the maximum 50 users to be added as admins.

Many repositories may be managed by bigger team with more than 50 users (with admin privileges).

What you expected to happen:
Increase the max limit to 200

How to reproduce it: