Lock file updates plus NumPy 2.4 fix in derived coord tests (#6876)

* Updated environment lockfiles

* Adapt tests for NumPy 2.4 scalar conversion - numpy/numpy#29841 .

---------

Co-authored-by: Lockfile bot <[email protected]>

Author: trexfeathers

docs/src/whatsnew/latest.rst

@@ -90,6 +90,9 @@ This document explains the changes made to Iris for this release
 #. `@trexfeathers`_ and `@hdyson`_ updated ``_ff_replacement.py`` to clarify
    that Iris supports Ancillaries. (:pull:`6792`)
 
+#. `@trexfeathers`_ adapted ``test_OceanSigmaZFactory`` for NumPy 2.4 - only
+   0-dimensional arrays can now be converted to scalars. (:pull:`6876`)
+
 
 .. comment
     Whatsnew author names (@github name) in alphabetical order. Note that,

lib/iris/tests/unit/aux_factory/test_OceanSigmaZFactory.py

@@ -179,7 +179,7 @@ def coord_dims(coord):
 
     @staticmethod
     def derive(sigma, eta, depth, depth_c, nsigma, zlev, coord=True):
-        nsigma_slice = slice(0, int(nsigma))
+        nsigma_slice = slice(0, nsigma.squeeze())
         temp = eta + sigma * (np.minimum(depth_c, depth) + eta)
         shape = temp.shape
         result = np.ones(shape, dtype=temp.dtype) * zlev