This reverts commit 74cf9e2573 "- Fix Firefox left-rigth scrollbar."
This reverts commit 9dd8216dfb.
"- Fix cards below swimlane title in Firefox by making
[previous fix](https://github.com/wekan/wekan/pull/2132/commits/f7c6b7fce237a6dbdbbd6d728cfb11ad3f4378eb)"
And this partially reverts commit dd88eb4cc
The root of the issue was that I was adding a new div and nesting
the list of lists in this new list. This resulted in some
weird behavior that Firefox could not handled properly
Revert to a code colser to v2.02, by just having the
swimlane header in a separate line, and keep only one
flex element.
fixes#2137