Ignore some warnings in CI workflow (#1671)
Ignore some warnings in CI workflow (#1671)

Ignore warnings produced by upload-artifact step if no files are
available to upload. Not all jobs in the matrix build are expected to
produce artifacts, so this isn't a problem worth warning about.

phrocker/accumulo-1,phrocker/accumulo-1,apache/accumulo,ctubbsii/accumulo,phrocker/accumulo-1,mjwall/accumulo,milleruntime/accumulo,apache/accumulo,mjwall/accumulo,ctubbsii/accumulo,milleruntime/accumulo,apache/accumulo,apache/accumulo,mjwall/accumulo,mjwall/accumulo,milleruntime/accumulo,ctubbsii/accumulo,milleruntime/accumulo,apache/accumulo,milleruntime/accumulo,milleruntime/accumulo,ctubbsii/accumulo,mjwall/accumulo,apache/accumulo,phrocker/accumulo-1,mjwall/accumulo,mjwall/accumulo,phrocker/accumulo-1,phrocker/accumulo-1,phrocker/accumulo-1,ctubbsii/accumulo,milleruntime/accumulo,ctubbsii/accumulo,apache/accumulo,ctubbsii/accumulo