@dario-zubovic
You can change this in WebGL player settings.
Goto Edit -> Project Settings -> Player
A inspector window for player settings will be shown. In that select WebGL https://docs.unity3d.com/Manual/class-PlayerSettingsWebGL.html
And then check `Publishing Settings` section and uncheck Data caching.
Also here is forum thread discussing the same issue.
https://forum.unity.com/threads/unitycache-indexeddb-database-could-not-be-opene...