Remove capacity setting in create Volume response

[boddumanohar]

Now that kubernetes-csi/external-provisioner#271 this PR is merged, we can depend on external-provisioner to set the capacity setting automatically.

What type of PR is this?
/kind cleanup

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

none

[k8s-ci-robot]

Hi @boddumanohar. Thanks for your PR.

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[coveralls]

Pull Request Test Coverage Report for Build 815618031

• 3 of 3 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 80.792%

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Totals
Change from base Build 806991648:	0.0%
Covered Lines:	551
Relevant Lines:	682

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💛 - Coveralls

[msau42]

/ok-to-test

[andyzhangx]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: andyzhangx, boddumanohar

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