Update the Homebrew librdkafka package version

The ./brew-update-pr.sh script in this directory updates the brew formula for librdkafka and pushes a PR to the homebrew-core repository.

You should run it in two steps, first an implicit dry-run mode to check that things seem correct, and if that checks out a live upload mode which actually pushes the PR.

# Do a dry-run first, v0.11.0 is the librdkafka tag:
$ ./brew-update-pr.sh v0.11.0

# If everything looks okay, run the live upload mode:
$ ./brew-update-pr.sh --upload v0.11.0