test: Reduce workers back to 2 in GithubActions
because the hardware won't be able to accommodate 3 clusters:
```
Hardware specification for Windows and Linux virtual machines:
2-core CPU
7 GB of RAM memory
14 GB of SSD disk space
```
# tests.
if [ -z ${CARRIER_ACCEPTANCE_KUBECONFIG+x} ]; then
#ginkgo -p -stream acceptance/.
- ginkgo -nodes 3 -stream acceptance/.
+ ginkgo -nodes 2 -stream acceptance/.
else
ginkgo acceptance/.
fi
