Update link to the Slack invite

Author: shakuzen

SUPPORT.adoc

@@ -19,4 +19,4 @@ https://stackoverflow.com/help/how-to-ask[advice on how to ask a good question].
 == Slack
 If you want to discuss something or have a question that isn't suited to Stack Overflow,
 the Micrometer community chat in the
-http://slack.micrometer.io/[micrometer-metrics channel on Slack].
+https://join.slack.com/t/micrometer-metrics/shared_invite/zt-ewo3kcs0-Ji3aOAqTxnjYPEFBBI5HqQ[micrometer-metrics Slack].