Revert "Merge branch 'rosulk-patch-12' into 'master'"

This reverts merge request !19250

app/assets/stylesheets/pages/boards.scss

@@ -80,7 +80,6 @@
   overflow-x: scroll;
   white-space: nowrap;
   min-height: 200px;
-  display: flex;
   @include media-breakpoint-only(sm) {
     height: calc(100vh - #{$issue-board-list-difference-sm});
@@ -111,15 +110,17 @@
 .board {
   display: inline-block;
-  flex: 1;
-  min-width: 300px;
-  max-width: 400px;
+  width: calc(85vw - 15px);
   height: 100%;
   padding-right: ($gl-padding / 2);
   padding-left: ($gl-padding / 2);
   white-space: normal;
   vertical-align: top;
+  @include media-breakpoint-up(sm) {
+    width: 400px;
+  }
+
   &.is-expandable {
     .board-header {
       cursor: pointer;
@@ -127,8 +128,6 @@
   }
   &.is-collapsed {
-    flex: none;
-    min-width: 0;
     width: 50px;
     .board-header {

changelogs/unreleased/rosulk-patch-12.yml

----
-title: Flex issue board columns
-merge_request: 19250
-author: Roman Rosluk
-type: changed