Fix protruded infomation board section in about/more page (#4415)

* Fix protruded infomation board section

Set "flexwrap: wrap" for sections. Set upper and lower padding for each section, and adjust clearances around sections accordingly. Settings for viewport threshold 500px is no more needed.

* Fix mistake of reducing information-board padding

In according with this fix, additional padding setting  for maximum 840px width is no more needed.