Trebuchet: Set 5x6 grid to 5 hotseat icons

* 5x5 and 5x7 have hotseat icon count 5 (matches column count)

* 5x6 currently has hotseat icon count set to 6 which does not
  look good with the column count of 5.

* The original commit message shows this was intentional:
  https://review.lineageos.org/q/Ib8d5dcc70d386376755c0a57b009ced1b2ee0834
  But a hotseat icon count of 5 for all of 5x5,5x6,5x7 looks more consistent.

Change-Id: Ic55a258b8ef64d10b7440576af87d0e78d318cc3