Move alert description validation to be optional

[assafad]

Many alert rules have summary annotation, but not description, and this is valid, since description is not mandatory. This PR moves the alert description validation to be optional.

[machadovilaca]

can you sign the commit @assafad?

[assafad]

can you sign the commit @assafad?

I think it's signed already, isn't it?

[machadovilaca]

I activated a mandatory signing option, but I think it is a different kind of singing
https://docs.github.com/en/authentication/managing-commit-signature-verification/about-commit-signature-verification vs https://docs.github.com/en/authentication/managing-commit-signature-verification/signing-commits

I'm removing the check