modules: partially revert commit 41ba9b31.

We don't need to build modules as .so files with the last 2 commits.
Just keep using shared_module() from commit 41ba9b31.

modules/meson.build

@@ -94,7 +94,5 @@ foreach module : modules
     link_args: link_args,
     install: true,
     install_dir: gimpplugindir / 'modules',
-    # Explicitly set .so suffix on macOS
-    name_suffix: host_machine.system() == 'darwin' ? 'so' : [],
   )
-endforeach
+endforeach