[ERROR]: Many doc pages still contain references to Slack

[ashkrisk]

Is there an existing issue for this?

• [X] I have searched the existing issues.

Issue

Many pages in the documentation encourage users to join the Slack channel. For example in the performance FAQ:

• Join our Slack Channel to find support and engage with our open-source community.

However, the Milvus community has moved to Discord and is no longer active on Slack.

Suggestion

The affected pages should be updated to promote the Discord server instead of the Slack channel.

Anything else?

Sample screenshot from the Performance FAQ page: