security/olm: update to 3.2.11, latest upstream

I missed six months of updates here -- portscout doesn't
seem to find GitLab-based releases for me. The release
notes are on all the tags pages, here's the latest:
	https://gitlab.matrix.org/matrix-org/olm/-/tags/3.2.11

Documentation builds now, that seems to be the important
line-item for us this release. 3.2.8 added a better error
description when a buffer is too small. 3.2.7 added better
handling of fallback keys.