Set aiohttp to >=3.7.4,<4

Avoid CVE-2021-21330

Author: fabaff

setup.py

@@ -27,7 +27,7 @@
     author='Fabian Affolter',
     author_email='[email protected]',
     license='MIT',
-    install_requires=['aiohttp<4', 'async_timeout<4'],
+    install_requires=['aiohttp>=3.7.4,<4', 'async_timeout<4'],
     packages=['luftdaten'],
     zip_safe=True,
     classifiers=[