Pin of `smmap<4` is undesirable

This pin was put in place to fix a dependency issue with package gitdb, which we don't provide, but depend on.

This can be undone when this (https://github.com/ContinuumIO/anaconda-issues/issues/12255) is fixed.

To undo this work, just revert !205 (merged).

mentioned in commit 2d04da36

mentioned in merge request !216 (merged)

closed via merge request !216 (merged)

mentioned in commit eb6a2d97