CI: Pin sphinx below `4.0.0` (#2772)
CI: Pin sphinx below `4.0.0` (#2772)


cloudera/ibis,cloudera/ibis,ibis-project/ibis,cpcloud/ibis,cpcloud/ibis,ibis-project/ibis,ibis-project/ibis,cpcloud/ibis,cloudera/ibis,ibis-project/ibis,cpcloud/ibis