Fix async assertions in test files (#1510)

* fix: await assertSnapshot in test files for async assertions

packages/rrweb-snapshot/test/integration.test.ts

@@ -153,7 +153,7 @@ describe('integration tests', function (this: ISuite) {
           'blob:http://localhost:xxxx/...',
         );
 
-      assertSnapshot(rebuildHtml);
+      await assertSnapshot(rebuildHtml);
     });
   }
 
@@ -427,7 +427,7 @@ describe('iframe integration tests', function (this: ISuite) {
       null,
       2,
     );
-    assertSnapshot(snapshotResult);
+    await assertSnapshot(snapshotResult);
   });
 });
 
@@ -470,6 +470,6 @@ describe('shadow DOM integration tests', function (this: ISuite) {
       null,
       2,
     );
-    assertSnapshot(snapshotResult);
+    await assertSnapshot(snapshotResult);
   });
 });