Fix group_saml_enforced_sso_new_account_spec:35 end-to-end test

What does this MR do?

Fixes ee/browser_ui/1_manage/group/group_saml_enforced_sso_new_account_spec.rb:35 spec:

1. Use user's full name instead of email address to click on the searched row. This is because the email address now links to mailto:.
2. Removes the docker image for the idp service as a first step in the after block. This is to avoid a lingering docker container incase a step in the after block fails.
3. Place the user_row_content selector on the row instead of the entire table and update selector sanity check file name.

Related issue: #330957 (closed)

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