Change in wording related to SAML experience

What does this MR do and why?

Correct confusing language related to the SAML linking experience.

Closes #271631 (closed)

Screenshots or screen recordings

See the proposed text here.

A few differences from the proposal worth mentioning:

Proposed	Implemented	Differences
		kept button's blue background instead of green kept compact vertical spacing
		kept button's blue background instead of green username is quoted email is parenthesised "organization" is lowercased

How to set up and validate locally

Some instructions on how to enable SAML in local development:

• https://gitlab.com/gitlab-org/gitlab-development-kit/blob/main/doc/howto/saml.md
• https://gitlab.com/gitlab-org/manage/authentication-and-authorization/discussion/-/issues/32#note_1002860588

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.