[META] Seven theme: Reevaluate capitalization of UI elements

[klonos]

This has been discussed during last week's dev meeting, with #3975 (comment) being the trigger for it.

• [UX] Remove uppercase transform on fieldset labels in Seven theme #4125 | Fieldset labels
• ... | Table: Header cells
• ... | Dropbuttons
• ... | Primary tabs
• ... | H2 in List themes page

[olafgrabienski]

I'm going to collect some uppercase examples in this thread (before opening separate issues) to get a first overview.

[olafgrabienski]

Table: header cells and dropbuttons are uppercase.

Example: Image styles page

See lowercase in comparison:

Btw, another advantage of lowercase: it needs less space. The dropbuttons on the image styles page had a min-width of 97px. With lowercase they need only 77px.

[olafgrabienski]

Primary tabs (and H2 in themes page) are uppercase.

Example: Appearance / List themes page:

Lowercase for comparison:

[stpaultim]

@klonos and @jenlampton - Is this an opportunity for a couple of "Good First Issue" issues?