chore(deps): update msgspec requirement from ~=0.18.5 to ~=0.18.6 (Pycord-Development#2328)

Updates the requirements on [msgspec](https://github.com/jcrist/msgspec) to permit the latest version.
- [Release notes](https://github.com/jcrist/msgspec/releases)
- [Commits](jcrist/msgspec@0.18.5...0.18.6)

---
updated-dependencies:
- dependency-name: msgspec
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

requirements/speed.txt

@@ -1,2 +1,2 @@
-msgspec~=0.18.5
+msgspec~=0.18.6
 aiohttp[speedups]