Add SECURITY.rst to doc files in selective checks

[potiuk]

The SECURITY.rst document is automatically included when in the documentation we publish and it should be spell-checked and verified by Sphinx whenever it is changed. Adding it to doc files will trigger docs build whenever it gets changed.

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Read the Pull Request Guidelines for more information.
In case of fundamental code changes, an Airflow Improvement Proposal (AIP) is needed.
In case of a new dependency, check compliance with the ASF 3rd Party License Policy.
In case of backwards incompatible changes please leave a note in a newsfragment file, named {pr_number}.significant.rst or {issue_number}.significant.rst, in newsfragments.

[potiuk]

I found it out when I merged #30960 accidentally

[hussein-awala]

Good catch