test: Minor change to increase the coverage

Running rootCmd.Execute is the same as Execute, but for coverage it has
a increate as it is a function declared in `cmd`.

Signed-off-by: Kairo de Araujo <[email protected]>

cmd/archivistactl/cmd/root_test.go

@@ -35,7 +35,7 @@ func (ut *UTRootSuite) Test_Root() {
 	rootCmd.SetOut(output)
 	rootCmd.SetErr(output)
 	rootCmd.SetArgs([]string{"help"})
-	err := rootCmd.Execute()
+	err := Execute()
 	if err != nil {
 		ut.FailNow(err.Error())
 	}