fix linter warnings

[fhennig]

there are a lot of these:

./src/web-components/visualization/gs-statistics.tsx

    'numeratorFilter' is not publicly accessible but is marked as a public property (@property). Use the '@internalProperty' decorator instead?
    23:  @property({ type: Object })
    no-property-visibility-mismatch

Sounds like it might be an easy fix? But maybe it's left as a non-internal property for an explicit reason - so I'm making a ticket for now.

[fengelniederhammer]

I didn't find an easy fix for these yet, but I never really looked into the issue. It might be that the linter reports false positives because it's rather unmaintained (and the issue doesn't exist on never versions of lit anymore).