chore: remove obsolete css vendor prefixes (#739)

Co-authored-by: Dominik Pschenitschni <mail@celement.de>
Reviewed-on: https://kolaente.dev/vikunja/frontend/pulls/739
Reviewed-by: konrad <k@knt.li>
Co-authored-by: dpschen <dpschen@noreply.kolaente.de>
Co-committed-by: dpschen <dpschen@noreply.kolaente.de>

src/styles/components/kanban.scss

@@ -62,12 +62,7 @@ $filter-container-height: '1rem - #{$switch-view-height}';
 			}
 
 			.task {
-				-webkit-touch-callout: none; // iOS Safari
-				-webkit-user-select: none; // Safari
-				-khtml-user-select: none; // Konqueror HTML
-				-moz-user-select: none; // Old versions of Firefox
-				-ms-user-select: none; // Internet Explorer/Edge
-				user-select: none; // Non-prefixed version, currently supported by Chrome, Opera and Firefox
+				user-select: none;
 
 				//transition: $ease-out;
 				cursor: pointer;