[bug] Route53.list_resource_record_sets not returning `IsTruncated`
`boto3` documentation specifies that `list_resource_record_sets` should return:
```python
'IsTruncated': True|False,
```
to indicate if results were truncated.

AWS API always returns this field, whether records are truncated or not. We rely on this field to know if we need to fetch more results, and using `@mock_route53` around this code fails due to missing field.

https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/route53.html#Route53.Client.list_resource_record_sets
diff --git a/moto/route53/responses.py b/moto/route53/responses.py
index 3e688b65d..077c89a2c 100644
--- a/moto/route53/responses.py
+++ b/moto/route53/responses.py
@@ -271,6 +271,7 @@ LIST_RRSET_RESPONSE = """<ListResourceRecordSetsResponse xmlns="https://route53.
       {{ record_set.to_xml() }}
    {% endfor %}
    </ResourceRecordSets>
+   <IsTruncated>false</IsTruncated>
 </ListResourceRecordSetsResponse>"""
 
 CHANGE_RRSET_RESPONSE = """<ChangeResourceRecordSetsResponse xmlns="https://route53.amazonaws.com/doc/2012-12-12/">
diff --git a/tests/test_route53/test_route53.py b/tests/test_route53/test_route53.py
index 0e9a1e2c0..746c78719 100644
--- a/tests/test_route53/test_route53.py
+++ b/tests/test_route53/test_route53.py
@@ -862,6 +862,8 @@ def test_list_resource_record_sets_name_type_filters():
         StartRecordName=all_records[start_with][1],
     )
 
+    response["IsTruncated"].should.equal(False)
+
     returned_records = [
         (record["Type"], record["Name"]) for record in response["ResourceRecordSets"]
     ]
['moto/route53/responses.py', 'tests/test_route53/test_route53.py']