Remove Babel from direct dependencies

cloudkitty-dashboard itself does not depends on Babel directly and uses
it via horizon.

Change-Id: Ifbc566f4bd93c27acaa15cf27155cad37b13f7e9

Author: kajinamit

requirements.txt

@@ -1,5 +1,7 @@
+# Requirements lower bounds listed here are our best effort to keep them up to
+# date but we do not test them so no guarantee of having them all correct. If
+# you find any incorrect lower bounds, let us know or propose a fix.
 pbr!= 2.1.0,>=2.0.0
-Babel>=1.3
 python-cloudkittyclient>=0.5.0
 horizon>=17.1.0 # Apache-2.0
 XStatic-D3>=3.5.17.0