Fix/Improve Mensa dish allergene parsing

[M4GNV5]

Describe the bug
Currently some allergene descriptions are parsed incorrectly and/or non-allergene declarations are parsed as allergenes.

To Reproduce
Compare https://www.max-manager.de/daten-extern/sw-erlangen-nuernberg/xml/mensa-ingolstadt.xml to https://dev.neuland.app/de/food/

Currently e.g.:
Gemüsesuppe ( So) mit Brötchen (Wz) turns into Gemüsesuppe ) mit Brötchen and the So allergene is even dropped / not included in our app

Expected behavior
Only known allergenes should be parsed, none should be dropped. Non-known (which probably never occurs, except in false positives) can remain in the name

Screenshots

Additional context

• https://github.com/neuland-ingolstadt/neuland.app/blob/develop/rogue-thi-app/pages/api/mensa.js#L57-L68
• https://github.com/neuland-ingolstadt/neuland.app/blob/develop/rogue-thi-app/data/allergens.json