F20: Update examples to reference python3

A previous CL updated dependent scripts to check for python >= 3.6 and
invoked python3 instead of python3.6. The updates to the markdown doc
were missed.

Update the markdown doc example to invoke the scripts using python3


Change-Id: I922f61d5d8c177aecbbb44d9c92473d7681abf1c
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/3104113
Tested-by: Jesse McGuire <jessemcguire@google.com>
Reviewed-by: Derek Beckett <dbeckett@chromium.org>
Commit-Queue: Jesse McGuire <jessemcguire@google.com>
1 file changed