ButtonElement: Remove `padding-top` and `padding-left` IE 7 notes
ButtonElement: Remove `padding-top` and `padding-left` IE 7 notes

Removing `padding-top` and `padding-left` IE 7 notes for icon- and
indicator-only ButtonElements.
In the current state, those rules are still useful for text-sizing
overrides in browser user preferences to scale icons.
Also replace wrong min size values and remove where not necessary.

Change-Id: I970767dd1a84376c9ad15d92f64c178283bb8c89

wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui