Cleanup type ignores in vertica provider where possible

[jscheffl]

Relates to #53241

[kyungjunleeme]

#53311

this case same case

        """Establish a connection to pinot broker through pinot dbapi."""
        conn = self.get_connection(self.pinot_broker_conn_id)  # type: ignore

        """Establish a connection to pinot broker through pinot dbapi."""
        conn = self.get_connection(self.get_conn_id())

get_conn_id() is a method defined in DbApiHook that dynamically returns the appropriate connection ID by referencing the value of self.conn_name_attr.

It's important to document these things well to prevent potential bugs.

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I noticed you had already investigated and added similar cases like this one, so I'm adding this as well. Thank you!
@jscheffl