build.yml: bump flatpak builder version

[kbdharun]

Type of change

• Bugfix (Change which fixes a issue)
• New feature (Change which adds new functionality)
• Enhancement (Change which slightly improves existing code)
• Breaking change (This change will introduce incompatibility with existing functionality)

Testing

• I have tested my changes and verified that they work as expected

How to test the changes

No information provided.

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[tfuxu]

Looks good to me, but I'll wait with merging your PR until all build workflows are finished

[tfuxu]

I'm putting your PR as a draft for now, as I want to investigate why aarch64 builds are taking so long to build.

[daudix]

Maybe I'm wrong but aarch64 builds are always long the first time, then it uses cache and builds fast (the build runs in vm so it slower)

[0xMRTT]

Yes 👍

[kbdharun]

Maybe I'm wrong but aarch64 builds are always long the first time, then it uses cache and builds fast (the build runs in vm so it slower)

Oh, that is possible.

[tfuxu]

This is probably the culprit of this issue: flatpak/flatpak-github-actions@56ddaec. From what I understand checking test CIs, a new action run (not a re-run) should have a different cache key, which should fix this issue. I'll merge this PR to check if this is true.