Need to return any error code from running antsibull-docs (#70763)

This way we fail early if there's a problem

hacking/build_library/build_ansible/command_plugins/docs_build.py

@@ -52,7 +52,7 @@ def generate_base_docs(args):
             f.write(yaml.dump(deps_file_contents))
 
         # Generate the plugin rst
-        antsibull_docs.run(['antsibull-docs', 'stable', '--deps-file', modified_deps_file,
+        return antsibull_docs.run(['antsibull-docs', 'stable', '--deps-file', modified_deps_file,
                                    '--ansible-base-cache', str(args.top_dir),
                                    '--dest-dir', args.output_dir])
 
@@ -107,7 +107,7 @@ def generate_full_docs(args):
             f.write(yaml.dump(deps_data))
 
         # Generate the plugin rst
-        antsibull_docs.run(['antsibull-docs', 'stable', '--deps-file', modified_deps_file,
+        return antsibull_docs.run(['antsibull-docs', 'stable', '--deps-file', modified_deps_file,
                                    '--ansible-base-cache', str(args.top_dir),
                                    '--dest-dir', args.output_dir])