Fix GO-2022-0969

[olivierlemasle]

govulncheck reports that prometheus-adapter is vulnerable to GO-2022-0969:

``` Vulnerability #1: GO-2022-0969 HTTP/2 server connections can hang forever waiting for a clean shutdown that was preempted by a fatal error. This condition can be exploited by a malicious client to cause a denial of service. Call stacks in your code: #1: for function Server.ServeConn sigs.k8s.io/prometheus-adapter/cmd/adapter.main cmd/adapter/adapter.go:353:19 sigs.k8s.io/custom-metrics-apiserver/pkg/cmd.AdapterBase.Run /home/olivier/gowork/pkg/mod/sigs.k8s.io/custom-metrics-apiserver@v1.24.0/pkg/cmd/builder.go:288:49 k8s.io/apiserver/pkg/server.preparedGenericAPIServer.Run /home/olivier/gowork/pkg/mod/k8s.io/apiserver@v0.24.3/pkg/server/genericapiserver.go:455:55 k8s.io/apiserver/pkg/server.preparedGenericAPIServer.NonBlockingRun /home/olivier/gowork/pkg/mod/k8s.io/apiserver@v0.24.3/pkg/server/genericapiserver.go:522:64 k8s.io/apiserver/pkg/server.SecureServingInfo.Serve /home/olivier/gowork/pkg/mod/k8s.io/apiserver@v0.24.3/pkg/server/secure_serving.go:211:18 k8s.io/apiserver/pkg/server.RunServer /home/olivier/gowork/pkg/mod/k8s.io/apiserver@v0.24.3/pkg/server/secure_serving.go:240:2 k8s.io/apiserver/pkg/server.RunServer$2 /home/olivier/gowork/pkg/mod/k8s.io/apiserver@v0.24.3/pkg/server/secure_serving.go:250:22 net/http.Server.Serve /usr/lib/golang/src/net/http/server.go:3102:3 net/http.conn.serve /usr/lib/golang/src/net/http/server.go:1899:7 golang.org/x/net/http2.ConfigureServer$1 /home/olivier/gowork/pkg/mod/golang.org/x/net@v0.0.0-20220425223048-2871e0cb64e4/http2/server.go:294:17 golang.org/x/net/http2.Server.ServeConn Found in: golang.org/x/net/http2@v0.0.0-20220425223048-2871e0cb64e4 Fixed in: golang.org/x/net/http2@v0.0.0-20220906165146-f3363e06e74c More info: https://pkg.go.dev/vuln/GO-2022-0969 ```

Updating golang.org/x/net to fix the issue.

/kind bug

[k8s-ci-robot]

@olivierlemasle: This issue is currently awaiting triage.

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[dgrisonnet]

/lgtm /approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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