Update watchfiles requirement from <0.21.0,>=0.16.1 to >=0.16.1,<0.22.0

Updates the requirements on [watchfiles](https://github.com/samuelcolvin/watchfiles) to permit the latest version.
- [Release notes](https://github.com/samuelcolvin/watchfiles/releases)
- [Commits](samuelcolvin/watchfiles@v0.16.1...v0.21.0)

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

Signed-off-by: dependabot[bot] <[email protected]>

pyproject.toml

@@ -98,7 +98,7 @@ dev = [
     "flake8>=5.0.4",
     "uvicorn[standard] >=0.19.0",
     "pre-commit>=2.17.0,<4.0.0",
-    "watchfiles>=0.16.1,<0.21.0",
+    "watchfiles>=0.16.1,<0.22.0",
 ]
 
 doc = [