graphs/modular_decomposition: trying to fix meson build

Author: cyrilbouvier

src/sage/graphs/graph_decompositions/meson.build

@@ -6,7 +6,7 @@ py.install_sources(
   'all.py',
   'all__sagemath_tdlib.py',
   'fast_digraph.pxd',
-  'modular_decomposition.py',
+  'modular_decomposition.pxd',
   'rankwidth.pxd',
   'slice_decomposition.pxd',
   'tree_decomposition.pxd',
@@ -38,6 +38,7 @@ endforeach
 extension_data_cpp = {
   'clique_separators': files('clique_separators.pyx'),
   'slice_decomposition' : files('slice_decomposition.pyx'),
+  'modular_decomposition' : files('modular_decomposition.pyx'),
 }
 
 foreach name, pyx : extension_data_cpp