Update msgspec requirement from <0.20,>=0.18 to >=0.18,<0.21

Updates the requirements on [msgspec](https://github.com/jcrist/msgspec) to permit the latest version.
- [Release notes](https://github.com/jcrist/msgspec/releases)
- [Changelog](https://github.com/jcrist/msgspec/blob/main/docs/changelog.md)
- [Commits](jcrist/msgspec@0.18.0...0.20.0)

---
updated-dependencies:
- dependency-name: msgspec
  dependency-version: 0.20.0
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

pyproject.toml

@@ -86,7 +86,7 @@ classifiers = [
 dependencies = [
     "requests>=2.21.0",
     "aiohttp>=3.9.2",
-    "msgspec>=0.18,<0.20",
+    "msgspec>=0.18,<0.21",
     "tenacity>=8,<10"
 ]