Double the client timeout

[jhrozek]

When talking to a remote mediator instance, sometimes the 5 seconds were
not enough. Let's increase the timeout.

Fixes: #1374

[jhrozek]

Flaky test:

❌ TestAll/TestHandleWebHookUnexistentRepoPackage (10ms)
      handlers_githubwebhooks_test.go:384: 
          	Error Trace:	/home/runner/work/mediator/mediator/internal/controlplane/handlers_githubwebhooks_test.go:384
          	Error:      	Received unexpected error:
          	            	Post "http://localhost:44033": dial tcp [::1]:44033: connect: connection refused
          	Test:       	TestAll/TestHandleWebHookUnexistentRepoPackage
          	Messages:   	failed to make request
      controller.go:269: missing call(s) to *mockdb.MockStore.GetRepositoryByRepoID(is anything, is anything) /home/runner/work/mediator/mediator/internal/controlplane/handlers_githubwebhooks_test.go:347
      controller.go:269: aborting test due to missing call(s)