Fix Zig 0.16 compatibility by replacing deprecated

[kalelidev]

Summary

Fix Zig 0.16 compatibility by replacing deprecated std.heap.GeneralPurposeAllocator with std.heap.DebugAllocator.
url: https://ziglang.org/documentation/0.16.0/#toc-Choosing-an-Allocator

Changes

Updated allocator declarations in zflecs.zig:

std.heap.GeneralPurposeAllocator(.{})

→

std.heap.DebugAllocator(.{})

Why

GeneralPurposeAllocator is no longer available in Zig 0.16 stdlib.

DebugAllocator is the supported replacement and provides equivalent allocator behavior for this use case.

No functional ECS behavior was changed.

Notes

deinit() logic was left unchanged since the current implementation compiles and behaves correctly with DebugAllocator.