almir: pin the sqlalchemy version used by zope.sqlalchemy to 8

Otherwise, sqlalchemy 9 is used which triggers iElectric/almir#61
pinning it to 7 caused a build error. This does mean that both versions
are on the PYTHONPATH, but it seems to work.

pkgs/top-level/python-packages.nix

@@ -309,8 +309,8 @@ let
       self.transaction
       self.waitress
       self.webhelpers
-      self.zope_sqlalchemy
       self.psycopg2
+      (self.zope_sqlalchemy.override rec {propagatedBuildInputs = with self; [ sqlalchemy8 transaction ];})
     ];
 
     postInstall = ''