add cond py-mpi4py dep to conduit (#17211)

var/spack/repos/builtin/packages/conduit/package.py

@@ -93,6 +93,7 @@ class Conduit(Package):
     depends_on("python", when="+python")
     extends("python", when="+python")
     depends_on("py-numpy", when="+python", type=('build', 'run'))
+    depends_on("py-mpi4py", when="+python+mpi", type=('build', 'run'))
 
     #######################
     # I/O Packages