Update changelog scripts to support the recently changed plugin tag convention

[sboschman]

What type of PR is this?

Uncomment one (or more) /kind <> lines:

/kind bug

/kind cleanup

/kind design

/kind documentation

/kind failing-test

/kind feature

Any specific area of the project related to this PR?

Uncomment one (or more) /area <> lines:

/area plugins

/area registry

/area build

/area documentation

What this PR does / why we need it:

Support changelog generation with the changed plugin tags (https://github.com/falcosecurity/plugins/issues/223)

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

[poiana]

LGTM label has been added.

Git tree hash: 55fabb6728f96e51729d8fe8a41e08f705d01704

[poiana]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: leogr, sboschman

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