remove duplicate code of add task spec annotation

[lowang-bh]

/kind cleanup

What this PR does / why we need it:

add volcano task spec annotation already done in decorator

Which issue(s) this PR fixes (optional, in Fixes #<issue number>, #<issue number>, ... format, will close the issue(s) when PR gets merged):
Fixes #

Checklist:

• Docs included if any changes are user facing

[coveralls]

Pull Request Test Coverage Report for Build 5353154045

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 11 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.01%) to 34.186%

---

Files with Coverage Reduction	New Missed Lines	%
pkg/controller.v1/mpi/mpijob_controller.go	11	78.86%

Totals
Change from base Build 5306620240:	0.01%
Covered Lines:	3369
Relevant Lines:	9855

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 5353620244

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.01%) to 34.165%

---

Files with Coverage Reduction	New Missed Lines	%
pkg/controller.v1/mpi/mpijob_controller.go	2	79.7%

Totals
Change from base Build 5306620240:	-0.01%
Covered Lines:	3367
Relevant Lines:	9855

---

💛 - Coveralls

[tenzen-y]

Thanks!
/lgtm
/assign @johnugeorge @gaocegege @terrytangyuan

[johnugeorge]

Thanks @lowang-bh

/lgtm
/approve

[johnugeorge]

/approve

[google-oss-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: johnugeorge, lowang-bh

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [johnugeorge]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment