gitian: install signapple in gitian-osx-signer.yml
gitian: install signapple in gitian-osx-signer.yml

Github-Pull: #20880
Rebased-From: 42bb1ea363286b088257cabccb686ef1887c1d3b

monacoinproject/monacoin,monacoinproject/monacoin,monacoinproject/monacoin,monacoinproject/monacoin,monacoinproject/monacoin,monacoinproject/monacoin