message: Remove gunan@ from platform/windows codeowners.
diff: /tensorflow/core/common_runtime/eager @qqfish @kkimdev
  /tenosrflow/core/debug @caisq
  /tensorflow/core/nccl/ @azaks2 @chsigg
  -/tensorflow/core/platform/windows/ @gunan @mihaimaruseac
  +/tensorflow/core/platform/windows/ @mihaimaruseac
  /tensorflow/lite/experimental/micro @petewarden @advaitjain
  /tensorflow/python/autograph/ @mdanatg @kkimdev
  /tensorflow/python/debug @caisq
  