Remove pin from pydantic

[masci]

Is your feature request related to a problem? Please describe.
We had several tests failing after the release of pydantic 1.10 and we pinned the version to an older one but we should stay up to date as that's an important dependency for Haystack.

Describe the solution you'd like
Remove the pin and fix the test failures (those are mostly related to the new dataclass decorator that we use e.g. in Document)

[danielbichuetti]

The main reason is related to some initialization pydantic do into dataclasses for his own internal logic. These extra fields were being mutated to Document.meta in reason of its logic.

One solution that I can see is filtering new pydantic current initialization variable.

I'll post a PR for it.