Remove parentheses around the root error

Author: dconeybe

packages/firestore/src/local/simple_db.ts

@@ -328,9 +328,8 @@ export class SimpleDb {
                 Code.FAILED_PRECONDITION,
                 'Unable to open an IndexedDB connection. This could be due to running in a ' +
                   'private browsing session on a browser whose private browsing sessions do not ' +
-                  'support IndexedDB. (' +
-                  error +
-                  ')'
+                  'support IndexedDB: ' +
+                  error
               )
             );
           } else {