Remove the cfg argument from Step.Execute [#67]

This is the first step toward removing run.Config entirely. InitKube was
the only Step that even used cfg in its Execute function; the rest just
discarded it.

internal/run/upgrade_test.go

@@ -93,7 +93,7 @@ func (suite *UpgradeTestSuite) TestPrepareAndExecute() {
 	cfg := Config{}
 	err := u.Prepare(cfg)
 	suite.Require().Nil(err)
-	u.Execute(cfg)
+	u.Execute()
 }
 
 func (suite *UpgradeTestSuite) TestPrepareNamespaceFlag() {