Use the same padding horizontally and vertically, so the views like readme look a bit nicer. Just slightly adjusted two values, nothing really test-able here.
## Motivation
I came to the conclusion that they should be the same myself, later I checked GitHub and it turned out to also use the same paddings. I would like to notice that the padding here (2em = 32px) is the same as GitHub uses too.
I find this as a logical UI change because the paddings are usually same on both axis across the UI (like on PR sidebar).
Also updated paddings for when the files are shown in profile, but copied the `1.5em` that GitHub uses. This, once again, makes sense, because the overview markdown isn't the primary content, or as primary as the readme on the repo is, taking the full usable width.
## Preview
https://codeberg.org/attachments/55f6685c-1978-410a-a17b-9fac91f0642e
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https://codeberg.org/attachments/d9016a1c-13cf-4ea6-a8e4-2619d93f3560
## Note
`.non-diff-file-content .plain-text` is left untouched with `1em 2em`, because the plaintext seems to add it's own margins, so it would make it look worse.
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/3944
Reviewed-by: Otto <otto@codeberg.org>
Reviewed-by: Beowulf <beowulf@noreply.codeberg.org>
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