Search: fix search product supporting determination

[kangzj]

Changes proposed in this Pull Request:

Fixes compatibility issue with old activation process.

Jetpack product discussion

p8oabR-Nm#comment-5892-p2

Does this pull request change what data or activity we track or use?

no

Testing instructions:

• Go to a fresh NJ site, connect it
• Ensure search is not supported
• Purchase search product
• Ensure search dashboard is available
• Ensure Instant Search works

[github-actions]

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[jeherve]

This seems to test well for me. 🚢

[jeherve]

• Cherry-picked to jetpack/branch-10.6 in 5ed3b4f
• planning a new release of the Search package in Search: release a new version of the package. #22523
• The release branch is now using the new packages as of 788b317