Correct the units in TURN servers expiry documentation (#2520)
Correct the units in TURN servers expiry documentation (#2520)

As shown elsewhere in client.ts, turnServersExpiry really is in
milliseconds rather than seconds. It seems that other libraries like
matrix-react-sdk were already expecting it to be in milliseconds
anyways, so it's just the documentation that was wrong.
matrix-org/matrix-js-sdk,matrix-org/matrix-js-sdk,matrix-org/matrix-js-sdk,matrix-org/matrix-js-sdk