helm/repository: copy loop iterator variable

Common mistake
(https://github.com/golang/go/wiki/CommonMistakes#using-goroutines-on-loop-iterator-variables),
but due to update now properly found by `go vet`.

Signed-off-by: Hidde Beydals <hidde@hhh.computer>

internal/helm/repository/oci_chart_repository_test.go

@@ -245,6 +245,7 @@ func TestOCIChartRepository_DownloadChart(t *testing.T) {
 	}
 
 	for _, tc := range testCases {
+		tc := tc
 		t.Run(tc.name, func(t *testing.T) {
 			g := NewWithT(t)
 			t.Parallel()