Remove fomantic header module (#30033)

Likely still a few useless classes left, but I think I at least don't
have missed any.

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Co-authored-by: delvh <dev.lh@web.de>
Co-authored-by: Giteabot <teabot@gitea.io>

web_src/fomantic/semantic.json

@@ -28,7 +28,6 @@
     "dimmer",
     "dropdown",
     "form",
-    "header",
     "input",
     "label",
     "list",