.circleci: Upgrade all xcode 9 workers to xcode 11 (#45153)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/45153
xcode 9 is being deprectated within circleci infra so we should get
everything else on a more recent version of xcode
Signed-off-by: Eli Uriegas <eliuriegas@fb.com>
Test Plan: Imported from OSS
Reviewed By: malfet
Differential Revision: D23852774
Pulled By: seemethere
fbshipit-source-id: c02e162f1993d408de439fee21b340e9640e5a24
