Do no use the ahash reimport (#4504)

<!--
Please read the "Making a PR" section of
[`CONTRIBUTING.md`](https://github.com/emilk/egui/blob/master/CONTRIBUTING.md)
before opening a Pull Request!

* Keep your PR:s small and focused.
* The PR title is what ends up in the changelog, so make it descriptive!
* If applicable, add a screenshot or gif.
* If it is a non-trivial addition, consider adding a demo for it to
`egui_demo_lib`, or a new example.
* Do NOT open PR:s from your `master` branch, as that makes it hard for
maintainers to add commits to your PR.
* Remember to run `cargo fmt` and `cargo clippy`.
* Open the PR as a draft until you have self-reviewed it and run
`./scripts/check.sh`.
* When you have addressed a PR comment, mark it as resolved.

Please be patient! I will review your PR, but my time is limited!
-->

Related to #3482 

Not sure what the "best practice" is, to me it seems like one should
import from "the original location" if possible, but now it should at
least be possible to not re-export ahash without any breakage in the
egui code base (but possibly in projects using egui, so one should
probably deprecate it if one would like to go that path). It also seems
like epaint re-exports ahash.

crates/eframe/Cargo.toml

@@ -129,6 +129,7 @@ egui = { workspace = true, default-features = false, features = [
   "log",
 ] }
 
+ahash.workspace = true
 document-features.workspace = true
 log.workspace = true
 parking_lot.workspace = true