Docs page has wrong Cursor.execute signature

[gitbuda]

https://memgraph.github.io/pymgclient/cursor.html#mgclient.Cursor.execute contains only param=None, the correct is execute(query, params=None).

[antaljanosbenjamin]

The first argument of every function is cropped. I assume because they should be the argument representing self. The same happens for fetchmany also. After adding a first "dummy" parameter, the docs page is rendered properly. I think we should check all doc strings and update them accordingly.