Bumps [MQTTnet.Extensions.ManagedClient](https://github.com/chkr1011/MQTTnet) from 3.0.12-rc1 to 3.0.12.
- [Release notes](https://github.com/chkr1011/MQTTnet/releases)
- [Commits](https://github.com/chkr1011/MQTTnet/commits/v3.0.12)
Signed-off-by: Ndependabot-preview[bot] <support@dependabot.com>