Fix firefox font smoothing to be consistent with chrome

packages/rocketchat-theme/client/imports/base.less

@@ -528,6 +528,7 @@ body {
 	height: 100%;
 	width: 100%;
 	-webkit-font-smoothing: antialiased;
+	-moz-osx-font-smoothing: grayscale;
 	line-height: 1rem;
 	padding: 0;
 	overflow: visible;