Remove a pin that is no longer needed

requirements/edx-sandbox/shared.in

@@ -16,13 +16,6 @@ pyparsing                           # Python parsing library; used by the calc p
 sympy==0.7.1                        # Symbolic math library; used by the calc package
 scipy==0.14.0                       # Math, science, and engineering library; used by the calc package
 
-# Pinned early:
-#   edx-sandbox/shared.in has cryptography, which wants idna, and finds 2.8
-#   paver.in has requests, which wants idna<2.8
-#       but paver.in includes edx-sandbox/shared.txt which now pins idna==2.8
-#       *conflict*
-idna<2.8
-
 # Install these packages from the edx-platform working tree
 # NOTE: if you change code in these packages, you MUST change the version
 # number in its setup.py or the code WILL NOT be installed during deploy.