[iOS][CI] Remove org-member from iOS Simulator Builds (#34410)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/34410
### Summary
Currently, the iOS jobs are not being run on PRs anymore. This is because all iOS jobs have specified the `org-member` as a context which used to include all pytorch members. But seems like recently this rule has changed. It turns out that only users from the admin group or builder group can have access right to the context values. https://circleci.com/gh/organizations/pytorch/settings#contexts/2b885fc9-ef3a-4b86-8f5a-2e6e22bd0cfe
This PR will remove `org-member` from the iOS simulator build which doesn't require code signing. For the arm64 builds, they'll only be run on master, not on PRs anymore.
### Test plan
- The iOS simulator job should be able to appear in the PR workflow
Test Plan: Imported from OSS
Differential Revision: D20347270
Pulled By: xta0
fbshipit-source-id: 23f37d40160c237dc280e0e82f879c1d601f72ac
