Erase needs of job in SingleWorkflow (#9)

Reviewed-on: https://gitea.com/gitea/act/pulls/9
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: Jason Song <i@wolfogre.com>
Co-committed-by: Jason Song <i@wolfogre.com>

pkg/jobparser/jobparser.go

@@ -50,6 +50,7 @@ func Parse(content []byte, options ...ParseOption) ([]*SingleWorkflow, error) {
 				runsOn[i] = evaluator.Interpolate(v)
 			}
 			job.RawRunsOn = encodeRunsOn(runsOn)
+			job.EraseNeeds() // there will be only one job in SingleWorkflow, it cannot have needs
 			ret = append(ret, &SingleWorkflow{
 				Name:     workflow.Name,
 				RawOn:    workflow.RawOn,