Remove unused code in aws cloud provider

[leakingtapan]

What type of PR is this?

Uncomment only one, leave it on its own line:

/kind api-change
/kind bug

/kind cleanup

/kind design
/kind documentation
/kind failing-test
/kind feature
/kind flake

What this PR does / why we need it:
Removed the logic related to instanceType which is not implemented and not used for real.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
None

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

None

[leakingtapan]

/cc @mcrute

[leakingtapan]

/sig storage

[mcrute]

It looks like this was introduced in edf0292 (March 2015) and hasn't been updated since then. I don't see any reason to keep it around.

/lgtm
/assign @justinsb

[justinsb]

So the one method on awsInstanceType was removed in e4dc670

So this is indeed no longer used.

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: justinsb, leakingtapan

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