Reduce size of "compiled" version

[matterhorn103]

The size of the app prepared with pyinstaller varies in size (107 MiB on Windows, 169 MiB on Linux) but is in any case quite larger.

Since this is pretty unnecessary, it would be worth looking at ways to reduce the size (e.g. only use PySide6-Essentials).

In particular it might be worth looking at using pyside6-deploy to produce actual binaries instead.

[matterhorn103]

Using only pyside6-essentials does reduce the footprint, surprisingly, to 149 MiB on Linux. Unfortunately this can't be set in pyinstaller.spec, it is entirely dependent on whether the environment has the full pyside6 installed in it or just pyside6-essentials. The dependency list was changed appropriately by d75627e.