* Changes the headings' rank of the security settings section
This commit changes the existing headings' rank of the security settings section from level 6 to level 4.
* Renames the auth.change_password string into auth.security
The "Security" preferences' section used to be called "Change password". When it was renamed, the string name wasn't changed.
This commits changes auth.change_password to auth.security.
* Adds a heading to the password change form
There was previously no heading for the part of the "Security" page that contain the password change form.
This commit adds a rank 4 heading to this section and reintroduces an "auth.change_password" string to be used inside it.
* Removes useless HR elements
The various sections of the "Security" settings page were previously separated by HR elements.
Now that there is proper headings, they're not required anymore.
* Updates CSS
This commit updates CSS in such a way that the same style is applied to all the H4 elements of the settings.
* Correct a mistake
A character went missing on one of the previous commits, broking the CSS.
This new commit fixes it.
* Fix font-weight for CJK fonts
* Use `font-weight: 700;` for mobile support
* Fix indentation
* Remove trailing whitespace
* Remove trailing whitespace
