Remove deprecated OCI image repositories in default ruleset

[maxgio92]

What type of PR is this?

/kind cleanup
/kind rule-update

Any specific area of the project related to this PR?

/area rules

What this PR does / why we need it:

Cleans up no longer valid references.

Which issue(s) this PR fixes:

Fixes #1633

Special notes for your reviewer:

The default Falco ruleset references (mostly to ignore the containers which runs with) OCI image repositories that are no longer available or maintained. One example is docker.io/sysdig/falco, which is replaced by docker.io/falcosecurity/falco.

Does this PR introduce a user-facing change?:

rule(list `falco_privileged_images`): remove deprecated Falco's OCI image repositories
rule(list `falco_sensitive_mount_images`): remove deprecated Falco's OCI image repositories
rule(macro `k8s_containers`): remove deprecated Falco's OCI image repositories

[leodido]

/milestone 0.28.1

[poiana]

LGTM label has been added.

Git tree hash: 598e9e2593ccfb6c40afa07855bf6b5765f4046b

[leodido]

@maxgio92 please populate the release notes :)

[leogr]

/approve

[poiana]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: leogr

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