golangci-lint: enable and fix thelper linter

Signed-off-by: Matthieu MOREL <matthieu.morel35@gmail.com>

internal/restartabletest/restartable_delegate.go

@@ -75,6 +75,7 @@ func RunRestartableDelegateTests(
 	newMock func() Mockable,
 	tests ...RestartableDelegateTest,
 ) {
+	t.Helper()
 	for _, tc := range tests {
 		t.Run(tc.Function, func(t *testing.T) {
 			p := new(MockRestartableProcess)

internal/velero/images_test.go

@@ -86,6 +86,7 @@ func TestImageRegistry(t *testing.T) {
 }
 
 func testDefaultImage(t *testing.T, defaultImageFn func() string, imageName string) {
+	t.Helper()
 	testCases := []struct {
 		name              string
 		buildInfoVersion  string