The dev branch of the rules_proto_grpc should to be replaced with the legacy branch

[try-agaaain]

I'm trying to build with an executing 'build.sh' file, but I'm getting an error like this:

                fail("error running '%s' while working with @%s:\n%s" % (command_text, name, stderr))
Error in fail: error running 'git fetch origin dev:origin/dev' while working with @rules_proto_grpc:
fatal: couldn't find remote ref dev
ERROR: Error computing the main repository mapping: no such package '@@rules_proto_grpc//': error running 'git fetch origin dev:origin/dev' while working with @rules_proto_grpc:
fatal: couldn't find remote ref dev

I found out that rules_proto_grpc 'dev' branch doesn't exist now, but there is a 'legacy' branch.

[jovany-wang]

@BryainZhang CC