Do not render filters documentation twice

doc/tools/build_modref_templates.py

@@ -51,6 +51,7 @@ if __name__ == '__main__':
     docwriter = ApiDocWriter(package)
     docwriter.package_skip_patterns += [r'\.fixes$',
                                         r'\.externals$',
+                                        r'filter$',
                                         ]
     docwriter.write_api_docs(outdir)
     docwriter.write_index(outdir, 'api', relative_to='source/api')