bump aiohttp version to <4

Signed-off-by: Florian Scherf <f.scherf@pengutronix.de>

Author: fscherf

setup.py

@@ -10,7 +10,7 @@
       url='https://github.com/pengutronix/aiohttp-json-rpc/',
       author_email='f.scherf@pengutronix.de',
       license='Apache 2.0',
-      install_requires=['aiohttp>=3,<3.6'],
+      install_requires=['aiohttp>=3,<4'],
       python_requires='>=3.5',
       packages=find_packages(),
       zip_safe=False,