chore(cli): address cli netcheck test flake (#13492)

* netcheck: removes check for healthy node report in test
* coderd/healthcheck/derphealth: do not override parent context deadline

cli/netcheck_test.go

@@ -5,7 +5,6 @@ import (
 	"encoding/json"
 	"testing"
 
-	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
 	"github.com/coder/coder/v2/cli/clitest"
@@ -30,7 +29,8 @@ func TestNetcheck(t *testing.T) {
 	var report healthsdk.DERPHealthReport
 	require.NoError(t, json.Unmarshal(b, &report))
 
-	assert.True(t, report.Healthy)
+	// We do not assert that the report is healthy, just that
+	// it has the expected number of reports per region.
 	require.Len(t, report.Regions, 1+1) // 1 built-in region + 1 test-managed STUN region
 	for _, v := range report.Regions {
 		require.Len(t, v.NodeReports, len(v.Region.Nodes))