Add RTLCSS rules for changes introduced in #3774 (#3807)

- This also deletes a redundant CSS background rule.

Co-authored-by: Poorchop <>

p/themes/Alternative-Dark/adark.css

@@ -271,7 +271,6 @@ a.btn {
 
 .nav-head {
 	margin: 0;
-	background: #fff;
 	background: #262626;
 	border-bottom: 1px solid #333;
 	text-align: right;

p/themes/Alternative-Dark/adark.rtl.css

@@ -271,9 +271,8 @@ a.btn {
 
 .nav-head {
 	margin: 0;
-	background: #fff;
-	background: linear-gradient(to bottom, #fff, #f0f0f0);
-	border-bottom: 1px solid #ddd;
+	background: #262626;
+	border-bottom: 1px solid #333;
 	text-align: left;
 }
 
@@ -1121,11 +1120,11 @@ a.btn {
 
 	.aside .toggle_aside,
 	#panel .close {
-		background: #f6f6f6;
+		background: #262626;
 		display: block;
 		width: 100%;
 		height: 50px;
-		border-bottom: 1px solid #ddd;
+		border-bottom: 1px solid #333;
 		line-height: 50px;
 		text-align: center;
 	}