Revert "Erase needs of job in SingleWorkflow (#9)" (#32)

This reverts commit 1ba076d321.

`EraseNeeds` Shouldn't be used in `jobparser.Parse`, it's for https://github.com/go-gitea/gitea/blob/023e61e678dc353fa6c9b0299c37f48e98a3c7af/models/actions/run.go#L200

Or Gitea won't be able to get `Needs` of jobs.

Reviewed-on: https://gitea.com/gitea/act/pulls/32
Reviewed-by: Zettat123 <[email protected]>

pkg/jobparser/testdata/has_needs.out.yaml

@@ -10,6 +10,7 @@ name: test
 jobs:
   job2:
     name: job2
+    needs: job1
     runs-on: linux
     steps:
       - run: uname -a
@@ -18,6 +19,7 @@ name: test
 jobs:
   job3:
     name: job3
+    needs: [job1, job2]
     runs-on: linux
     steps:
       - run: uname -a