fix: rendering errors (missing key and h3 child of TableHeader)

[LaumiH]

The charging table page showed two errors:

1. The table did not have unique keys/ identifiers for every row due to wrapping each TableRow in a fragment (<>...</>), which doesn't pass the key prop down to the actual TableRow component.
2. The table header was not correctly using the <h3> tag, which cannot be a direct child of TableHead

I fixed these errors, sorry for the small PR.

[ianchen0119]

Hi @LaumiH

Thanks for your contribution!