Fix bug in get_group_masters

[oskooi]

Fixes a bug in the function get_group_masters of simulation.py which is recently causing a failure in the CI (reproduced below). This bug occurs in Numpy 1.24 which removed a deprecation warning for np.bool.

Elapsed run time = 0.3249 sERROR: test_divide_parallel_processes (__main__.TestDivideParallelProcesses)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/runner/work/meep/meep/build/meep-1.26.0-beta/_build/sub/python/../../../python/tests/test_divide_mp\
i_processes.py", line 53, in test_divide_parallel_processes
    tot_fluxes = mp.merge_subgroup_data(tot_flux)
  File "/home/runner/work/meep/meep/build/meep-1.26.0-beta/_build/sub/python/meep/simulation.py", line 6078, in m\
erge_subgroup_data
    group_masters = get_group_masters()
  File "/home/runner/work/meep/meep/build/meep-1.26.0-beta/_build/sub/python/meep/simulation.py", line 6045, in g\
et_group_masters
    group_master_idx = np.zeros((num_workers,), dtype=np.bool)
  File "/opt/hostedtoolcache/Python/3.10.9/x64/lib/python3.10/site-packages/numpy/__init__.py", line 284, in __ge\
tattr__
    raise AttributeError("module {!r} has no attribute "
AttributeError: module 'numpy' has no attribute 'bool'

[codecov-commenter]

Codecov Report

Merging #2349 (4099531) into master (6e44cb8) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##           master    #2349   +/-   ##
=======================================
  Coverage   72.55%   72.55%           
=======================================
  Files          17       17           
  Lines        5156     5156           
=======================================
  Hits         3741     3741           
  Misses       1415     1415           

Impacted Files	Coverage Δ
python/simulation.py	76.62% <0.00%> (ø)