[9.18] fix: ci: Revert "Capture scripts for Coverity Scan analysis"

This reverts commit b4a2674d98902983e8096c99b747343482d30673.

The --fs-capture-search option is no more. The ability to analyse Python
scripts in Coverity turned out to be questionable anyways.

Closes #5456

Backport of MR !10808

Merge branch 'backport-5456-coverity-scan-drop-fs-capture-search-option-9.18' into 'bind-9.18'

See merge request isc-projects/bind9!10811