chore: reset jsii-rosetta worker count to default

This value was reduced as part of troubleshooting of various Node Worker memory
issues. These issues are theorized to have been mitigated by #16752. Our pack
time is currently over 2 hours, compared to 20-30 minutes prior to the set of
changes. By removing this worker count override, we should be able to get back
to normal pack times and speed up the pipeline.

pack.sh

@@ -5,7 +5,6 @@
 set -eu
 export PATH=$PWD/node_modules/.bin:$PATH
 export NODE_OPTIONS="--max-old-space-size=8192 ${NODE_OPTIONS:-}"
-export JSII_ROSETTA_MAX_WORKER_COUNT="${JSII_ROSETTA_MAX_WORKER_COUNT:-8}"
 root=$PWD
 
 # Get version and changelog file name (these require that .versionrc.json would have been generated)