refactor: remove debug error output

Errors should always be logged with an error level and not debug level.
Since the error is returned here, it will be logged later as an error.
Presumably this was a leftover from debugging the executor chain in:
PR: nektos#971

Author: ZauberNerd

pkg/common/executor.go

@@ -136,7 +136,6 @@ func (e Executor) Then(then Executor) Executor {
 			case Warning:
 				log.Warning(err.Error())
 			default:
-				log.Debugf("%+v", err)
 				return err
 			}
 		}