Remove mention that H2 is not recommended for large installations
Remove mention that H2 is not recommended for large installations

Since 2.16, most data is stored in NoteDB apart from one table.

So instead of wasting resources by having a mysql db we can 
convert to H2 for that single table.

But the documentation recommend against it for large installations.

Change-Id: I54e8ceb825292fd7b651f7d44deb594e2fc0ebc6

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