Update minimum Python version in Readme

Author: elacuesta

README.md

@@ -22,7 +22,7 @@ to integrate `asyncio`-based projects such as `Playwright`.
 
 ### Minimum required versions
 
-* Python >= 3.8
+* Python >= 3.9
 * Scrapy >= 2.0 (!= 2.4.0)
 * Playwright >= 1.15