fix(offline): Fix server certificate error when trying to delete stor…

…ed content (#6080)

Fixes #6079

lib/offline/session_deleter.js

@@ -71,14 +71,6 @@ shaka.offline.SessionDeleter = class {
       return [];
     }
 
-    try {
-      await drmEngine.setServerCertificate();
-    } catch (e) {
-      shaka.log.warning('Error setting server certificate', e);
-      await drmEngine.destroy();
-      return [];
-    }
-
     /** @type {!Array.<string>} */
     const sessionIds = [];
     await Promise.all(bucket.sessionIds.map(async (sessionId) => {