Bump build number to rebuild osx-64

osx-64 build failed when merging into main because libcxx was updated from 16.x.x
to 17.x.x between the time of the MR and the merge.
libcxx 17.x.x requires MacOS >=10.13 (see conda-forge/libcxx-feedstock#131)

My understanding is that a re-render should fix it due to conda-forge/conda-forge-pinning-feedstock#5829

recipe/meta.yaml

@@ -10,7 +10,7 @@ source:
   sha256: 483894b3272b6c7d457d193f2a31bd417083fc9035b6965c43fd32223a3f6a4b
 
 build:
-  number: 3
+  number: 4
   script: '{{ PYTHON }} -m pip install . --no-deps --ignore-installed --no-cache-dir -vvv '
 
 requirements: