fix(turbo-persistence): allow 32-bit usize conversion (#97288)
### What?
Change the pointer-width assertion in `usize_from_u32` from `<` to `<=`,
allowing the conversion to compile on 32-bit targets.
### Why?
The surrounding comment states that Turbopack assumes a pointer width of
at least 32 bits, but the strict comparison rejects exactly 32-bit
targets. Since `u32` and `usize` have the same width on these targets,
the conversion remains lossless.
This currently causes `rspack-turbo-persistence` to fail to compile with
`error[E0080]` in Rspack's [`i686-pc-windows-msvc` CI
job](https://github.com/web-infra-dev/rspack/actions/runs/31665978273/job/94340544786#step:25:446).
### How?
Allow equal source and target bit widths in the compile-time assertion.
