Revert "Relax CI constraint on numpy<1.25 (Qiskit#11020)"

Removing the restriction on the numpy version has introduced some
non-determinism to some of the unitary synthesis tests that is causing a
flaky failure in CI. This commit reverts the version cap removal to
unblock CI. In parallel we should debug the source of the instability
causing the test to fail so we can run CI using the latest version of
numpy.

This reverts commit fb8a69d.

constraints.txt

@@ -2,6 +2,11 @@
 # 4.0+. The pin can be removed after nbformat is updated.
 jsonschema==3.2.0
 
+# Numpy 1.25 deprecated some behaviours that we used, and caused the isometry
+# tests to flake. See https://github.com/Qiskit/qiskit-terra/issues/10305,
+# remove pin when resolving that.
+numpy<1.25
+
 # 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.