[GH Actions] Remove "Install Yarn" step from Android workflows
Summary:
This step is no longer necessary since Yarn 1.22.19 is included on Ubuntu 22.04 runners:
(https://github.com/actions/runner-images/blob/main/images/linux/Ubuntu2204-Readme.md#package-management)
Test Plan: Removed step on fork and observed that subsequent yarn ci-cleaninstall step succeeded.
Reviewers: ashoat, tomek, marcin, jon, ginsu
Reviewed By: ashoat
Subscribers: michal
Differential Revision: https://phab.comm.dev/D8687