chore: remove Kubernetes 1.6 heapster version from VHD script

[mboersma]

Reason for Change:

heapster:v1.3.0 was included in the VHD image, but it is only needed by Kubernetes 1.6 which is available for legacy ACS support.

Issue Fixed:

Requirements:

• uses conventional commit messages
• includes documentation
• adds unit tests
• tested upgrade from previous version

Notes:

[CecileRobertMichon]

/lgtm

[acs-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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[codecov]

Codecov Report

Merging #233 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #233   +/-   ##
=======================================
  Coverage   53.23%   53.23%           
=======================================
  Files          95       95           
  Lines       14240    14240           
=======================================
  Hits         7580     7580           
  Misses       5994     5994           
  Partials      666      666