bug: `np.alltrue` will be deprecated in numpy 2.0

[mnfienen]

Describe the bug
flopy.plot.PlotMapView.contour_array is using np.alltrue at line 287 which will be deprecated in numpy 2.0

To Reproduce
Steps to reproduce the behavior:
Run the plotting functions at the end of this notebook
https://github.com/DOI-USGS/python-for-hydrology/blob/main/notebooks/part1_flopy/solutions/06-Project-voronoi.ipynb

Expected behavior
No deprecation warning

Screenshots
If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: OSX

[wpbonelli]

Looks like we got all these

$ grep -R np.alltrue --exclude-dir=.git
.docs/md/version_changes.md:* [fix(numpy 2.0 deprecation)](https://github.com/modflowpy/flopy/commit/ad35b8dda86959f8cdf4560934ab5f309dc28d56): Replace np.alltrue with np.all (#2088). Committed by mnfienen on 2024-02-04.