fix readFileAlloc usage

[tazend]

Hi,

just came across this project and tried to compile it with zig 0.15.1, and I got two errors in manifest/util where readFileAlloc was used. Essentially:

• path and Allocator arguments were swapped
• .limited64 returns a "Limit" enum in 0.15.1 now, just do with @min directly what .limited64 actually does.

Now everything compiles fine :).

[Cohors1316]

If you want a functioning version to use you'll have to run 0.14 for the moment. The tests are still failing for 0.15, but I'm pretty sure there's just one more issue to track down.

The issues with readFileAlloc are because the function signature annoyingly changed in 0.16. I've given up on 0.16 for now and am just trying to get a working 0.15 build.

That change is the only thing not backwards compatible throughout all of jetzig and it annoys me to no end.