Use white review icon in OL.

services/web/public/stylesheets/app/editor/review-panel.less

@@ -902,6 +902,13 @@
 	}
 }
 
+.review-icon when (@is-overleaf) {
+	background-position-y: -60px;
+	.toolbar .btn-full-height:hover & {
+		background-position-y: -60px;
+	}
+}
+
 .resolved-comments-toggle {
 	font-size: 14px;
 	color: lighten(@rp-type-blue, 25%);