Make the importlib_metadata requirement unconditional

Author: rpanderson

setup.cfg

@@ -26,7 +26,7 @@ packages = find:
 python_requires = >=3.6
 install_requires =
   blacs>=2.7.0
-  importlib_metadata ; python_version<'3.8'
+  importlib_metadata
   labscript>=2.6.0
   labscript_utils>=2.13.2
   numpy>=1.15.1