Remove fomantic loader module (#26670)
Replace Fomantic `loader` CSS module with our existing `is-loading`
spinner. Only three places in the UI used this module, which are
pictured here:
imagediff:
<img width="1237" alt="Screenshot 2023-08-22 at 22 18 01"
src="https://github.com/go-gitea/gitea/assets/115237/b0d82531-f05e-43c6-9e5b-1bfc268c056d">
webauthn:
<img width="894" alt="Screenshot 2023-08-22 at 22 05 05"
src="https://github.com/go-gitea/gitea/assets/115237/7b583425-d944-474a-a57a-22a65bbd8b29">
heatmap (I removed the previous loading text, it was unreadable because
it was tiny and on fast machines only visible for a fraction of a
second):
<img width="764" alt="Screenshot 2023-08-22 at 22 18 44"
src="https://github.com/go-gitea/gitea/assets/115237/1c7472d6-3e17-4224-a992-d8c0b380cc73">
Also, heatmap container does not resize any more after loading now and
previous duplicate id `user-heatmap` is gone.
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Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
8b5c081d76