Update UI text for require auth in MR policies

Problem to solve

The compliance team has introduced SAML SSO as an alternative option for users to require passwords on MR approvals. See SAML SSO authentication for merge request approval (&11084) or !130204 (merged).

In merge request policies the UI text still has Require the user's password to approve

Proposal

Update the UI text on merge request policies to Require user re-authentication (password or SAML) to approve