Pin codeql actions usage to latest 3.x. These were previously pointing
to `@2` which pulls in the latest v2 as they are released, with the
potential to break our workflows if a breaking change or malicious
version on the `@2` stream is ever pushed.
Changing this to a pinned version also means that dependabot will keep
this in the pinend version format (e.g., referencing a SHA) when it
opens a PR to bump the dependency.
The breaking change between v2 and v3 is that v3 requires Node 20 which
is a non-issue as we are running this on ubuntu latest.
Updates #cleanup
Signed-off-by: Mario Minardi <mario@tailscale.com>