clean: helm v2 logic code (#736)

Signed-off-by: yxxhero <aiopsclub@163.com>

pkg/helmexec/exec_test.go

@@ -13,8 +13,6 @@ import (
 	"github.com/Masterminds/semver/v3"
 	"github.com/google/go-cmp/cmp"
 	"go.uber.org/zap"
-
-	"github.com/helmfile/helmfile/pkg/envvar"
 )
 
 // Mocking the command-line runner
@@ -901,13 +899,6 @@ func Test_IsHelm3(t *testing.T) {
 	if !helm.IsHelm3() {
 		t.Error("helmexec.IsHelm3() - Failed to detect Helm 3")
 	}
-
-	t.Setenv(envvar.Helm3, "1")
-	helm2Runner = mockRunner{output: []byte("Client: v2.16.0+ge13bc94\n")}
-	helm = New("helm", false, NewLogger(os.Stdout, "info"), "dev", &helm2Runner)
-	if !helm.IsHelm3() {
-		t.Errorf("helmexec.IsHelm3() - Helm3 not detected when %s is set", envvar.Helm3)
-	}
 }
 
 func Test_GetPluginVersion(t *testing.T) {