Refactor/simplify Promises in MatrixRTCSession (#4466)
* Refactor/simplify Promises in MatrixRTCSession
* Update src/matrixrtc/MatrixRTCSession.ts
Co-authored-by: Hugh Nimmo-Smith <hughns@users.noreply.github.com>
* Fix+document+test leaveRoomSession's return value
* Throw instead of using expect in teardown
because lint rules forbid using expect outside of test functions
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Co-authored-by: Hugh Nimmo-Smith <hughns@users.noreply.github.com>
