In order to have a dedicate chat room for tree issues with a high signal to noise ratio, we've separated out a new tree-gardener channel from the tree-status channel on Discord. This updates the gardener docs to reference the new human-centric tree-gardener chat.

I've removed the line suggesting that people avoid spamming the room with requests for "when will this be resolved?" and "can I get an update?" since the doc is aimed mostly at the gardener themself and and not likely being read by those on chat asking "when will the tree be fixed?" Recently this hasn't been a source of noise.

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
• I signed the CLA.
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is test-exempt.
• I followed the breaking change policy and added Data Driven Fixes where supported.
• All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel on Discord.