fix: use disableDifferentialDownload flag in the AppImageBuilder

[peter-sanderson]

Hi, this is my first contribution here so please LMK if I did something wrong.

• I have a quite trouble running the tests. It produces a lot of errors that seem unrelated.
• I was able to run pnpm compile && TEST_FILES=linuxUpdaterTest.ts pnpm ci:test and it passed
• It also seems there is missing a test for AppImage (test AppImage download) is commented and not working

[changeset-bot]

🦋 Changeset detected

Latest commit: 03652f9

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
electron-updater	Patch

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[mmaietta]

Quick update: PR looks good! Just to double-check, did you test the full update process locally with a packaged app on your dev machine? Or was it only the unit tests? I need to double check if there's a differential update unit test for linux

[peter-sanderson]

@mmaietta Hi, what I did was that I have build the app and rsynced the out directory into node_modules in my app. That worked in a sense, that it processed the update by not using the differential flow.

About tests, as mentioned, I was not able to run them all. So I run selectively the linuxUpdaterTest.ts. That passed but it does not test the AppImage.

I also found and run differentialUpdateTest.ts it passes as well.