Improve email text part

What does this MR do?

In the text email part, we had HTML tags. So i changed that to make sure text email part contain only text and not HTML.

This part used a function to display the URL which allow to request a new token link. But now, the only part that use this function is the HTML email part. So I have deleted the function and directly added the code to generate the token.

In the text email part, i found that the condition to change the first message was missing. I borrowed the code from the HTML part and added it to the text part.

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation created/updated or follow-up review issue created
• [-] Code review guidelines
• [-] Merge request performance guidelines
• [-] Style guides
• [-] Database guides
• [-] Separation of EE specific content

Performance and testing

• [-] Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team