ci: 👷 lint code to MediaWiki standards

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resources/mixins.less

@@ -133,7 +133,7 @@
 		height: 100%;
 		content: '';
 		background-color: var( --color-surface-0 );
-		filter: opacity( 0.90 );
+		filter: opacity( 0.9 );
 		backdrop-filter: saturate( 50% ) blur( 16px );
 	}
 }

skinStyles/extensions/Echo/ext.echo.special.less

@@ -79,7 +79,7 @@
 		margin-bottom: var( --space-md );
 		overflow-x: auto;
 		background-color: var( --color-surface-0 );
-		filter: opacity( 0.90 );
+		filter: opacity( 0.9 );
 		backdrop-filter: saturate( 50% ) blur( 16px );
 		border-bottom: 1px solid var( --border-color-base );
 		box-shadow: none;