Update Docker example, to use more recent theia-traceviewer extension

[marcdumais-work]

The Docker example application is meant to be stable, and so it does not use the latest theia-traceviewer extension, built from master, but rather a hardcoded, npm-published older version known to be stable and working well.

The extension currently used in the Docker example is over 6 months old and could benefit from being updated, along with the version of the Theia framework used for the application itself (currently 1.45.1 - they must remain aligned). Currently, Theia v1.49.2 is used for the other (testing) example apps in this repo, and we are going to publish a new version of the extension soon, meant to work with the latest Theia community release (v1.52.0). I think it's a good opportunity to update the Docker example to use the version, used foir testing, that we are moving away from - v1.49.1 - that's known to be stable and well tested, at this point.