docs: Update requirements to mention Python 3.6 instead of 2.6.

As pointed out by Adam Mizerski.

Change-Id: I1a14b0cb3bb0e54313b68e957318d5049b9431b4
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/apitrace/+/2224524
Reviewed-by: Po-Hsien Wang <pwang@chromium.org>
Commit-Queue: Robert Tarasov <tutankhamen@chromium.org>
Tested-by: Robert Tarasov <tutankhamen@chromium.org>
1 file changed