Update base RubySAML library with SAML Request signing

[bramleyjl]

In #46092 the Identity team created a forked version of the RubySAML repository to fix a one-character bug. We should create a PR to have our update merged into the main repository so that we can continue to depend on it and receive other changes as they occur.

https://app.zenhub.com/workspaces/identity-5f5bab705a94c9001ba33734/issues/department-of-veterans-affairs/va.gov-team/46092

[bramleyjl]

Merge PR with base Ruby-SAML gem repository: SAML-Toolkits/ruby-saml#647

We're now waiting on approval from the SAML-Toolkits team that manages the gem.

[bramleyjl]

Merge PR to base Ruby SAML library: SAML-Toolkits/ruby-saml#650

We can now revert our gemfile to refer to the base version of Ruby SAML