Removes hash after the url when clicking Meta Data

Removes that hash appended to the URL when clicking Meta Data in post settings.

Closes #4386

When clicking 'Meta Data' the click event appends a # to the URL. I replaced the a with a button element so that won't happen anymore. The button has a type attribute because it will try and submit the form without it. Added text-align: left to the navlist button because the button centers it's content by default.


If `.nav-list-item` had the style, but `button` has a conflicting inherited style, it would use the inherited style.
By having `.nav-list-item button`, it is forced to use the desired style by virtue of having a heavier selector.