Remove SQLAlchemy pre-requisite as setup.py will already install it

Installing trino-python-client with the sqlalchemy extra like `pip
install trino[sqlalchemy]` automatically installs required version of
SQLAlchemy.

Author: hashhar

README.md

@@ -48,7 +48,6 @@ rows for example `Cursor.fetchone()` or `Cursor.fetchmany()`. By default
 
 **Prerequisite**
 
-- SQLAlchemy >= 1.3
 - Trino server >= 351
 
 **Installation**