[issue_tracker] Email format cleanup

[skarya22]

Brief summary of changes

• Updated the issue tracker emails to be a bit prettier

Testing instructions (if applicable)

1. Change your project/Config.xml to have sandbox 0 so that emails are sent
2. Add a User with a valid email address that you have access to as a Watcher to an issue and make a change. Confirm that the email is sent and looks okay
3. Now add that User as an assignee and modify the issue. Confirm that the email is sent and looks okay

Link(s) to related issue(s)

• Resolves [issue tracker] - email notification modifications #9906