i15-1: Turn swmr on the nexus writer

We're getting errors on analysis that say the file is open. We should be able to get around this with SMWR

We can turn this on by changing our yaml (see https://gitlab.diamond.ac.uk/daq/d2acq/services/nexus-file-converter/-/blob/master/src/main/resources/application.yaml#L22)

## Acceptance Criteria
- SWMR is turned on and we see if this fixes analysis

Start with the application.yaml configuration at the referenced line in the nexus-file-converter service. Check how SWMR is configured, enable it, and verify whether analysis no longer reports that the file is open.

Written by the indexing model from the issue text.