Improve account validation test coverage

[rebecca-shoptaw]

Closes #9542.

Feature. Adds more test cases to cover formatting checks for email and username fields in realtime_account_validation.js

Technical

Very simple! Basically reused the existing password test structure, also removed an unnecessary check re: required class.

Happy to add any further unit tests here that would be helpful as part of the same PR!

Testing

1. Run the JavaScript tests
2. All tests should pass, and the test coverage for realtime_account_validation.js should now be 75%.

Screenshot

Stakeholders

@cdrini

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 16.65%. Comparing base (1cd8f21) to head (f027411).
Report is 57 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #9543      +/-   ##
==========================================
+ Coverage   16.17%   16.65%   +0.47%     
==========================================
  Files          90       90              
  Lines        4736     4786      +50     
  Branches      824      829       +5     
==========================================
+ Hits          766      797      +31     
- Misses       3453     3470      +17     
- Partials      517      519       +2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[cdrini]

Nice! Lgtm 🥳