chore: Update matrix-sdk and switch to SQLite store

Hopefully this reduces our resources usage (not measured), but a test shows this strongly reduces the amount of data written to disk.

Todo:

• Clean up sessions using the sled store (we should probably start versioning the sessions so it is easier to make changes in the future).
• Upstream PR is merged and wait probably for another one that makes the SQLite store the default instead of sled.

Fixes Fractal is continously writing to disk (#1046 - closed).