Bump uvloop from 0.20.0 to 0.21.0

Bumps [uvloop](https://github.com/MagicStack/uvloop) from 0.20.0 to 0.21.0.
- [Release notes](https://github.com/MagicStack/uvloop/releases)
- [Commits](MagicStack/uvloop@v0.20.0...v0.21.0)

---
updated-dependencies:
- dependency-name: uvloop
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

requirements.txt

@@ -15,7 +15,7 @@ pyopenssl==24.2.1
 pyffish==0.0.84
 sortedcollections==2.1.0
 python-gettext==5.0
-uvloop==0.20.0 ; sys_platform == 'linux'
+uvloop==0.21.0 ; sys_platform == 'linux'
 objgraph==3.6.2
 black==24.10.0
 flake8==7.1.1