Add `flex: 0 0 auto` to some components to avoid bugs on iOS9 (#3313)

app/javascript/styles/components.scss

@@ -60,6 +60,7 @@
 
 .column-collapsable {
   position: relative;
+  flex: 0 0 auto;
 
   .column-collapsable__content {
     overflow: auto;
@@ -1792,6 +1793,7 @@
 
 .getting-started__wrapper {
   position: relative;
+  flex: 0 0 auto;
 }
 
 .getting-started__footer {