docs(RELEASE.md): correct slack channel URL

Signed-off-by: Leonardo Grasso <me@leonardograsso.com>

release.md

@@ -4,7 +4,7 @@ Our release process is partially automated using [CircleCI](https://app.circleci
 
 When we release we do the following process:
 
-1. We decide together (usually in the #falco channel in [slack](https://sysdig.slack.com)) what's the next version to tag
+1. We decide together (usually in the #falco channel in [slack](https://kubernetes.slack.com/messages/falco)) what's the next version to tag
 2. A person with repository rights does the tag
 3. The same person runs commands in their machine following the "Release commands" section below
 4. Once the CI has done its job, the tag is live on [Github](https://github.com/falcosecurity/falco-exporter/releases) with the artifacts, and the container image is live on [DockerHub](https://hub.docker.com/r/falcosecurity/falco-exporter) with proper tags
@@ -16,4 +16,4 @@ Tag the version
 ```bash
 git tag -a v0.1.0-rc.0 -m "v0.1.0-rc.0"
 git push origin v0.1.0-rc.0
-```
+```