stream-ui: Change view from 2-column to 1-column at width 992px.

This prevents the elements to go on a newline on iPad sized devices.

static/styles/settings.css

@@ -1784,7 +1784,7 @@ body:not(.night-mode) #settings_page .custom_user_field .datepicker {
 
 /* This value needs to match with the same in subscriptions.css, as
    we have some shared styles declared there */
-@media (width < $md_min) {
+@media (width < $lg_min) {
     #settings_overlay_container {
         /* this variable allows JavaScript to detect this media query */
         --single-column: yes;

static/styles/subscriptions.css

@@ -1119,7 +1119,7 @@ ul.grey-box {
 
    Longer-term we should extract this logic two-column-overlay class
    to read more naturally. */
-@media (width < $md_min) {
+@media (width < $lg_min) {
     .subscriptions-container {
         position: relative;
         overflow: hidden;