Bump max heap size in ci
Bump max heap size in ci

I have noticed that sbt runs better on my computer with 2G of heap.
Assuming we have that much memory on github actions, it seems like a
good idea to increase it there as well.

sbt/sbt,mdedetrich/sbt,mdedetrich/sbt,mdedetrich/sbt,mdedetrich/sbt,sbt/sbt,mdedetrich/sbt,sbt/sbt,mdedetrich/sbt,xuwei-k/xsbt,xuwei-k/xsbt,mdedetrich/sbt,sbt/sbt,sbt/sbt,sbt/sbt,sbt/sbt,xuwei-k/xsbt,xuwei-k/xsbt,xuwei-k/xsbt