Bump golang.org/x/net from 0.20.0 to 0.21.0

Bumps [golang.org/x/net](https://github.com/golang/net) from 0.20.0 to 0.21.0.
- [Commits](golang/net@v0.20.0...v0.21.0)

---
updated-dependencies:
- dependency-name: golang.org/x/net
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

go.mod

@@ -2,4 +2,4 @@ module healthcheck
 
 go 1.20
 
-require golang.org/x/net v0.20.0
+require golang.org/x/net v0.21.0

go.sum

@@ -1,2 +1,2 @@
-golang.org/x/net v0.20.0 h1:aCL9BSgETF1k+blQaYUBx9hJ9LOGP3gAVemcZlf1Kpo=
-golang.org/x/net v0.20.0/go.mod h1:z8BVo6PvndSri0LbOE3hAn0apkU+1YvI6E70E9jsnvY=
+golang.org/x/net v0.21.0 h1:AQyQV4dYCvJ7vGmJyKki9+PBdyvhkSd8EIx/qb0AYv4=
+golang.org/x/net v0.21.0/go.mod h1:bIjVDfnllIU7BJ2DNgfnXvpSvtn8VRwhlsaeUTyUS44=