fix(bug): Remove email from query param when clicking Change email

[vbudhram]

Because

• When users change their email address during sign-in or sign-up, the application should clear any prefilled email from the query parameters to avoid confusion and ensure the correct email is used.

This pull request

• Updates the sign-in and sign-up flows to remove the email query parameter from the URL when users choose to change their email address.
• Ensures that the navigation back to the entry page (/) includes any remaining query parameters except for email.
• Updates related tests to expect the new navigation behavior.

Issue that this pull request solves

Closes: https://mozilla-hub.atlassian.net/browse/FXA-11938
Closes: https://mozilla-hub.atlassian.net/browse/FXA-12010

Checklist

• My commit is GPG signed.
• If applicable, I have modified or added tests which pass locally.
• I have added necessary documentation (if appropriate).
• I have verified that my changes render correctly in RTL (if appropriate).

Screenshots (Optional)

Please attach the screenshots of the changes made in case of change in user interface.

Other information (Optional)