Replace owner with first_owner in A-F EE specs

What does this MR do and why?

We're moving towards Owner role being possible in Projects. Because multiple owners will be possible soon, we are phasing out owner.

This replaces project.owner with project.first_owner in some EE specs. This assumes that "any owner" will be okay, so the first one is chosen.

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MR acceptance checklist

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Related to #350603 (closed)