Merge remote-tracking branch 'remotes/origin/fix-column-headers-accessibility'

app/javascript/styles/mastodon/components.scss

@@ -2350,6 +2350,19 @@
   position: relative;
   z-index: 2;
   outline: 0;
+  overflow: hidden;
+
+  & > button {
+    display: flex;
+    flex: auto;
+    margin: 0;
+    border: none;
+    padding: 0;
+    color: inherit;
+    background: transparent;
+    font: inherit;
+    text-align: left;
+  }
 
   &.active {
     box-shadow: 0 1px 0 rgba($ui-highlight-color, 0.3);