Remove setup.py branch (#4203)

diff --git a/setup.py b/setup.py
index 4d7f5c2..0d71520 100644
--- a/setup.py
+++ b/setup.py
@@ -43,7 +43,7 @@
 
 VECTORS_DEPENDENCY = "cryptography_vectors=={0}".format(about['__version__'])
 
-setup_requirements = []
+setup_requirements = ["cffi>=1.7,!=1.11.3"]
 
 if platform.python_implementation() == "PyPy":
     if sys.pypy_version_info < (5, 3):
@@ -51,8 +51,6 @@
             "cryptography is not compatible with PyPy < 5.3. Please upgrade "
             "PyPy to use this library."
         )
-else:
-    setup_requirements.append("cffi>=1.7,!=1.11.3")
 
 test_requirements = [
     "pytest>=3.2.1,!=3.3.0",