update gn_to_cmake's minimim required cmake version
update gn_to_cmake's minimim required cmake version

Change-Id: I86f157b8d5885f1bf4cc013fc8e58d64dc1ba66e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/395096
Reviewed-by: Ben Wagner <53965154ffeecc4a10886eab9259e95965f2979a@google.com>
Commit-Queue: Herb Derby <9e12a3d2bbf73546e47cc9958f6ba8f3215b7eaf@google.com>

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