Remove more unused Fomantic variants (go-gitea#25292)

Save another 50KB of CSS by removing unused and useless Fomantic
variants.

Removed the last instance if a `tertiary` button and fixed a TODO:

<img width="509" alt="Screenshot 2023-06-15 at 22 34 36"
src="https://github.com/go-gitea/gitea/assets/115237/8a16ae7b-2b17-439b-a096-60a52724e3d6">

.gitattributes

@@ -5,5 +5,6 @@
 /templates/swagger/v1_json.tmpl linguist-generated
 /vendor/** -text -eol linguist-vendored
 /web_src/fomantic/build/** linguist-generated
+/web_src/fomantic/_site/globals/site.variables linguist-language=Less
 /web_src/js/vendor/** -text -eol linguist-vendored
 Dockerfile.* linguist-language=Dockerfile

web_src/css/modules/button.css

@@ -197,22 +197,6 @@ a.btn:hover {
   border-color: var(--color-secondary-active);
 }
 
-/* tertiary */
-
-.ui.tertiary.button,
-.ui.tertiary.button:focus {
-  color: var(--color-text-light);
-  border: none;
-}
-
-.ui.tertiary.button:hover {
-  color: var(--color-text);
-}
-
-.ui.tertiary.button:active {
-  color: var(--color-text-dark);
-}
-
 /* red */
 
 .ui.red.labels .label,

web_src/fomantic/_site/globals/site.variables

@@ -5,16 +5,17 @@
 @bold: 500;
 @useCustomScrollbars: false;
 @disabledOpacity: var(--opacity-disabled);
-@variationPopupTooltip: false;
 @linkHoverUnderline: underline;
-@variationButtonSocial: false;
 @pageOverflowX: visible;
 
-/* disable all inverted variations */
 @variationAccordionInverted: false;
 @variationBreadcrumbInverted: false;
+@variationButtonAnimated: false;
+@variationButtonAnimatedFade: false;
 @variationButtonAttached: false;
 @variationButtonInverted: false;
+@variationButtonSocial: false;
+@variationButtonTertiary: false;
 @variationCalendarInverted: false;
 @variationCardInverted: false;
 @variationCheckboxInverted: false;
@@ -25,25 +26,36 @@
 @variationFeedInverted: false;
 @variationFlyoutInverted: false;
 @variationFormInverted: false;
+@variationFormTransparent: false;
+@variationGridDoubling: false;
 @variationGridInverted: false;
 @variationHeaderInverted: false;
 @variationIconInverted: false;
 @variationInputInverted: false;
 @variationItemInverted: false;
+@variationLabelCorner: false;
+@variationLabelImage: false;
 @variationLabelInverted: false;
+@variationLabelRibbon: false;
+@variationLabelTag: false;
 @variationListInverted: false;
 @variationMenuInverted: false;
 @variationMessageInverted: false;
 @variationModalInverted: false;
 @variationNagInverted: false;
 @variationPlaceholderInverted: false;
 @variationPopupInverted: false;
+@variationPopupTooltip: false;
 @variationProgressInverted: false;
 @variationSegmentInverted: false;
+@variationSegmentPiled: false;
+@variationSegmentStacked: false;
 @variationSliderInverted: false;
 @variationStatisticInverted: false;
 @variationStepInverted: false;
 @variationTableInverted: false;
+@variationTableMarked: false;
+@variationTableStackable: false;
 @variationTextInverted: false;
 @variationToastInverted: false;
 @variationTransitionInverted: false;