Admin reskin: Remove line-height from input fields.

`line-height` values that were previously used to match the height of input fields affect the height of the background shown when text inside those fields is selected. Removing these `line-height` declarations allows the text selection highlight to render more naturally.

Additionally, update the height of the custom Date/Time format input fields on the General Settings screen to `32px` to align with the new design system.

Props arkaprabhachowdhury, audrasjb, hmrisad, huzaifaalmesbah, manhar, manishxdp, noruzzaman, ozgursar, r1k0, sachinrajcp123, wildworks.

Fixes #64763.

git-svn-id: https://develop.svn.wordpress.org/trunk@62171 602fd350-edb4-49c9-b593-d223f7449a82