chore: Update `@nextcloud/stylelint-config` and fix issues detected

Signed-off-by: Ferdinand Thiessen <opensource@fthiessen.de>

package.json

@@ -94,7 +94,7 @@
     "@nextcloud/babel-config": "^1.0.0",
     "@nextcloud/browserslist-config": "^2.3.0",
     "@nextcloud/eslint-config": "^8.3.0-beta.0",
-    "@nextcloud/stylelint-config": "^2.3.0",
+    "@nextcloud/stylelint-config": "^2.3.1",
     "@nextcloud/webpack-vue-config": "github:nextcloud/webpack-vue-config#master",
     "@vue/test-utils": "^1.3.0",
     "@vue/tsconfig": "^0.4.0",

src/components/NcAppNavigation/NcAppNavigation.vue

@@ -146,7 +146,6 @@ export default {
 	// Set scoped variable override
 	// Using --color-text-maxcontrast as a fallback evaluates to an invalid value as it references itself in this scope instead of the variable defined higher up
 	--color-text-maxcontrast: var(--color-text-maxcontrast-background-blur, var(--color-text-maxcontrast-default));
-
 	transition: transform var(--animation-quick), margin var(--animation-quick);
 	width: $navigation-width;
 	position: relative;

src/components/NcButton/NcButton.vue

@@ -540,7 +540,6 @@ export default {
 		color: var(--color-main-text);
 		background-color: transparent;
 		&:hover:not(:disabled) {
-			background-color: var(--color);
 			background-color: var(--color-background-hover);
 		}
 	}