remove metadata conversion

[aryanA101a]

Fixes #188

[aryanA101a]

@rgaudin Sorry, my bad. Actually, I ran the tests after the modification but didn't install the project.

[kelson42]

@aryanA101a Any update?

[rgaudin]

converted to draft to prevent accidental merge

[benoit74]

I don't think this is sufficient: type hints should be simplified as well to explicitly mention these methods support only bytes and str values now (i.e. conversion must be done by python-scraperlib or any other "user")

[rgaudin]

Thank you @benoit74 ; that's right and I forgot @aryanA101a to mention that you should not force-push after having asked for a review ; it makes (and made in that case) reviewing a real pain.

[rgaudin]

@aryanA101a please update type hints as suggested