Revert "More clearly specify how we look for v6 notebook packages"

This commit caused the *notebook* downstream version check
to fail, which makes sense?

This reverts commit 40029a7.

Author: yuvipanda

jupyter_server/prometheus/metrics.py

@@ -10,16 +10,13 @@
 
 try:
     from notebook._version import version_info as notebook_version_info
-    v6_notebook_present = notebook_version_info != server_version_info
 except ImportError:
-    # notebook._version is not present, so notebook v6 can not be present
-    v6_notebook_present = False
+    notebook_version_info = None
 
 
-if v6_notebook_present:
+if notebook_version_info is not None and notebook_version_info < (7,) and notebook_version_info != server_version_info:
     print("yes, we think we have an unshimmed notebook package")
     print(notebook_version_info)
-    print(server_version_info)
     # Jupyter Notebook v6 also defined these metrics.  Re-defining them results in a ValueError,
     # so we simply re-export them if we are co-existing with the notebook v6 package.
     # See https://github.com/jupyter/jupyter_server/issues/209