Update edx.org theme to add new css rule

* To make language selection button in footer consistent
with the edx.org theme, add new css rule
* Remove unused event from select element

LEARNER-1338

themes/edx.org/lms/static/sass/partials/lms/theme/_extras.scss

@@ -21,3 +21,15 @@
     }
   }
 }
+.select-lang-button {
+    padding: 3px;
+    color: $m-blue-d3 !important;
+    height: 30px;
+
+    &:hover,
+    &:active,
+    &:focus {
+        background: $m-blue-d3 !important;
+        color: white !important;
+    }
+}

themes/edx.org/lms/static/sass/partials/lms/theme/_variables.scss

@@ -1,3 +1,5 @@
 // Override theming for edx.org bootstrap
 
+$m-blue-d3: rgb(18, 111, 154) !default;
+
 @import 'edx-bootstrap/sass/edx/theme';