Removes direct URL requirements from cirq[dev-env] (#4249)

Removes direct URL requirements from cirq[dev-env].

Fixes #4222.
This is hard to test automatically as it would need to involve uploading to test pypi which in turn requires secrets on Github Actions (see #4247).

Author: balopat

setup.py

@@ -54,7 +54,9 @@
 requirements = [f'{p.name}=={p.version}' for p in modules.list_modules()]
 
 dev_requirements = explode('dev_tools/requirements/deps/dev-tools.txt')
-dev_requirements = [r.strip() for r in dev_requirements]
+
+# filter out direct urls (https://github.com/pypa/pip/issues/6301)
+dev_requirements = [r.strip() for r in dev_requirements if "git+http" not in r]
 
 setup(
     name=name,