Revert "Defaulting HIP_PLATFORM to amd on Windows"

[pfultz2]

Reverts #3466

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.04%. Comparing base (2c2085d) to head (d7e5728).
Report is 1 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #3476   +/-   ##
========================================
  Coverage    92.04%   92.04%           
========================================
  Files          506      506           
  Lines        20872    20872           
========================================
  Hits         19212    19212           
  Misses        1660     1660           

Flag	Coverage Δ
	92.04% <ø> (ø)

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