stylelint: Enable selector-pseudo-element-colon-notation

Via stylelint --fix

Change-Id: Ic1625ae755233e172cc6db734dc21ed2c5b377d8

.stylelintrc.json

@@ -2,7 +2,6 @@
 	"extends": "stylelint-config-wikimedia",
 	"rules": {
 		"unit-disallowed-list": null,
-		"declaration-property-unit-disallowed-list": null,
-		"selector-pseudo-element-colon-notation": null
+		"declaration-property-unit-disallowed-list": null
 	}
 }

modules/ext.RevisionSlider.lazy.less

@@ -49,8 +49,8 @@ https://codepen.io/Volker_E/pen/yqNXMe */
 	margin: 60px auto;
 
 	.mw-revslider-bounce,
-	&:before,
-	&:after {
+	&::before,
+	&::after {
 		content: '';
 		background-color: #72777d;
 		display: block;
@@ -62,12 +62,12 @@ https://codepen.io/Volker_E/pen/yqNXMe */
 		animation-delay: -160ms;
 	}
 
-	&:before {
+	&::before {
 		margin-right: 4px;
 		animation-delay: -330ms;
 	}
 
-	&:after {
+	&::after {
 		margin-left: 4px;
 		animation-delay: 0s;
 	}