Use valid security report schema for fixtures

What does this MR do and why?

Continuation of !116695 (merged).

In !116538 (merged) we're removing support for security report schema versions 14-x-x.

This MR prepares for the change by replacing schema version 14-1-0 with 15-0-0 in the relevant spec file.

The deprecation announcement was done in %15.3: !92137 (merged).

Related to #366478 (closed)

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MR acceptance checklist

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Related to #366478 (closed)