Update README.md

Removed asyncio:
Since asyncio is part of the Python standard library (available in Python 3.x), it doesn't need to be listed in requirements.txt.

Added aiohttp:
aiohttp is a third-party package required for making asynchronous HTTP requests, and it's not part of the standard library.

README.md

@@ -85,7 +85,7 @@ This release introduces several major updates to the Pokémon Battle script, imp
 4. **Constants and Validation**: Introduced constants for common values (e.g., experience thresholds) to make the code more maintainable. Added validation for missing or invalid data to prevent crashes during runtime.
 
 ### Dependencies:
-- `asyncio` for asynchronous requests.
+- `aiohttp` Required for making asynchronous HTTP requests.
 
 ### Installation:
 To install the dependencies, run the following command: