Boost: remove ISA

[kraftbj]

Fixes HOG-210

Proposed changes:

• Removes ISA from the code base.

Other information:

• Have you written new tests for your changes, if applicable?
• Have you checked the E2E test CI results, and verified that your changes do not break them?
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Jetpack product discussion

Linear

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

No.

Testing instructions:

• Ensures everything builds.
• Click through to ensure no random references or links remain.

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[jp-launch-control]

Code Coverage Summary

Coverage changed in 6 files. Only the first 5 are listed here.

File	Coverage	Δ%	Δ Uncovered
projects/plugins/boost/app/class-jetpack-boost.php	71/124 (57.26%)	-2.91%	6 💔
projects/plugins/boost/app/lib/class-premium-features.php	21/25 (84.00%)	-0.62%	0 💚
projects/plugins/boost/app/assets/src/js/features/image-guide/image-guide.tsx	0/5 (0.00%)	0.00%	-2 💚
projects/plugins/boost/app/assets/src/js/pages/index/index.tsx	0/13 (0.00%)	0.00%	-3 💚
projects/plugins/boost/app/assets/src/js/pages/purchase-success/purchase-success.tsx	0/9 (0.00%)	0.00%	-6 💚

Full summary · PHP report · JS report

_{Coverage check overridden by I don't care about code coverage for this PR Use this label to ignore the check for insufficient code coveage. .}

[LiamSarsfield]

LGTM! I gave it a whirl on JN and no issues were found.