Relax CI constraint on jsonschema

This was originally added because of `nbformat` using deprecated
functionality.  The constraint is causing installation problems for some
of our optionals now, particularly on Python 3.12, and should be fixed
by now anyway.

constraints.txt

@@ -1,7 +1,3 @@
-# jsonschema pinning needed due nbformat==5.1.3 using deprecated behaviour in
-# 4.0+. The pin can be removed after nbformat is updated.
-jsonschema==3.2.0
-
 # Scipy 1.11 seems to have caused an instability in the Weyl coordinates
 # eigensystem code for one of the test cases.  See
 # https://github.com/Qiskit/qiskit-terra/issues/10345 for current details.