Repair DevTools button padding by centralizing styles

This moves the padding styles for dialog content to the .mx_Dialog rule. In
addition, it fixes vector-im/riot-web#7548 where the DevTools buttons had double
padding.

Signed-off-by: J. Ryan Stinnett <jryans@gmail.com>

res/css/views/dialogs/_UnknownDeviceDialog.scss

@@ -20,9 +20,6 @@ limitations under the License.
     // is a pain in the ass. plus might as well make the dialog big given how
     // important it is.
     height: 100%;
-
-    // position the gemini scrollbar nicely
-    padding-right: 58px;
 }
 
 .mx_UnknownDeviceDialog {
@@ -51,4 +48,4 @@ limitations under the License.
 .mx_UnknownDeviceDialog .mx_UnknownDeviceDialog_deviceList li {
     height: 40px;
     border-bottom: 1px solid $primary-hairline-color;
-}
+}