Increanse Jenkins max heap for 1.3G to 1.5G
Increanse Jenkins max heap for 1.3G to 1.5G

The fix to partest to make it compile files in subdirectories means that
we're compiling more things and using more heap and has resulted in
tests failing with OutOfMemoryError. Hopefully this fixes that.

som-snytt/dotty,som-snytt/dotty,lampepfl/dotty,dotty-staging/dotty,lampepfl/dotty,dotty-staging/dotty,som-snytt/dotty,dotty-staging/dotty,lampepfl/dotty,dotty-staging/dotty,sjrd/dotty,sjrd/dotty,lampepfl/dotty,dotty-staging/dotty,sjrd/dotty,sjrd/dotty,lampepfl/dotty,som-snytt/dotty,som-snytt/dotty,sjrd/dotty