Turn off fail-fast.
Turn off fail-fast.

https://help.github.com/en/actions/reference/workflow-syntax-for-github-actions#jobsjob_idstrategyfail-fast

Fixes #997

thomasvl/swift-protobuf,thomasvl/swift-protobuf,apple/swift-protobuf,apple/swift-protobuf,tbkka/swift-protobuf,apple/swift-protobuf,tbkka/swift-protobuf,cburrows/swift-protobuf,apple/swift-protobuf,cburrows/swift-protobuf,thomasvl/swift-protobuf,tbkka/swift-protobuf,cburrows/swift-protobuf,apple/swift-protobuf,cburrows/swift-protobuf,thomasvl/swift-protobuf,tbkka/swift-protobuf,cburrows/swift-protobuf,cburrows/swift-protobuf,thomasvl/swift-protobuf,apple/swift-protobuf,thomasvl/swift-protobuf,cburrows/swift-protobuf,tbkka/swift-protobuf,thomasvl/swift-protobuf,tbkka/swift-protobuf,apple/swift-protobuf,tbkka/swift-protobuf