fix build table for ppc64le (#39475)
Summary:
This corrects the build info for ppc64le in the main README.
I am opening this PR before renaming the build job. (So, the "live" master README has the correct "live" link and the PR does not.)
Immediately after submitting the PR, I will correct the name of the build job. This will make the new PR link correct, and the current "master" link will briefly appear broken until this PR gets merged.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/39475
Differential Revision: D21883184
Pulled By: malfet
fbshipit-source-id: 148353b632448c98e5aff560d31642328afe7963
