fix: catalog-techdoc-url-reader should hand unmodified http rc (#1376)

Author: gabemontero

workspaces/ai-integrations/plugins/catalog-techdoc-url-reader-backend/src/plugin.ts

@@ -34,7 +34,7 @@ import {
   LoggerService,
 } from '@backstage/backend-plugin-api';
 import { Config } from '@backstage/config';
-import { NotFoundError } from '@backstage/errors';
+import { NotFoundError, NotModifiedError } from '@backstage/errors';
 import { Readable } from 'stream';
 import fs from 'fs';
 import platformPath from 'path';
@@ -174,6 +174,9 @@ export class ModeCatalogBridgeTechdocUrlReader implements UrlReaderService {
     if (response.status === 404) {
       throw new NotFoundError(message);
     }
+    if (response.status === 304) {
+      throw new NotModifiedError();
+    }
     throw new Error(message);
   }