safe one if clause (intersection is already false-y)

repo2docker/buildpacks/base.py

@@ -554,7 +554,6 @@ class BaseImage(BuildPack):
             ))
         except FileNotFoundError:
             pass
-        if self.stencila_contexts:
         if {'py', 'pyjp'}.intersection(self.stencila_contexts):
             assemble_scripts.extend(
                 [