Update halfbrown requirement from 0.3 to 0.4

Updates the requirements on [halfbrown](https://github.com/Licenser/halfbrown) to permit the latest version. <details> <summary>Commits</summary> <ul> <li><a href="https://github.com/Licenser/halfbrown/commit/9747ebbf39a0780ab6f97cd310cb0a3940ee71dd"><code>9747ebb</code></a> chore: Release halfbrown version 0.4.0</li> <li><a href="https://github.com/Licenser/halfbrown/commit/00f4146554a55ce35ad4002a8174587ebf2839ee"><code>00f4146</code></a> update to newest rust edituin</li> <li><a href="https://github.com/Licenser/halfbrown/commit/cc5a664b889e9264fbb467fefc0c1b4668b5d796"><code>cc5a664</code></a> Update hashbrown to latest</li> <li>See full diff in <a href="https://github.com/Licenser/halfbrown/compare/v0.3.0...v0.4.0">compare view</a></li> </ul> </details> <br /> Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting `@dependabot rebase`. [//]: # (dependabot-automerge-start) [//]: # (dependabot-automerge-end) --- <details> <summary>Dependabot commands and options</summary> <br /> You can trigger Dependabot actions by commenting on this PR: - `@dependabot rebase` will rebase this PR - `@dependabot recreate` will recreate this PR, overwriting any edits that have been made to it - `@dependabot merge` will merge this PR after your CI passes on it - `@dependabot squash and merge` will squash and merge this PR after your CI passes on it - `@dependabot cancel merge` will cancel a previously requested merge and block automerging - `@dependabot reopen` will reopen this PR if it is closed - `@dependabot close` will close this PR and stop Dependabot recreating it. You can achieve the same result by closing it manually - `@dependabot show <dependency name> ignore conditions` will show all of the ignore conditions of the specified dependency - `@dependabot ignore this major version` will close this PR and stop Dependabot creating any more for this major version (unless you reopen the PR or upgrade to it yourself) - `@dependabot ignore this minor version` will close this PR and stop Dependabot creating any more for this minor version (unless you reopen the PR or upgrade to it yourself) - `@dependabot ignore this dependency` will close this PR and stop Dependabot creating any more for this dependency (unless you reopen the PR or upgrade to it yourself) </details>