Remove @Persistent from MongoDB entity scanning

This commit removes `org.springframework.data.annotation.Persistent`
from the annotation types used for MongoDB entity scanning to align
with Spring Data MongoDB.

Fixes gh-25797

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/data/mongo/city/PersistentEntity.java

@@ -0,0 +1,28 @@
+/*
+ * Copyright 2012-2021 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.autoconfigure.data.mongo.city;
+
+import java.io.Serializable;
+
+import org.springframework.data.annotation.Persistent;
+
+@Persistent
+public class PersistentEntity implements Serializable {
+
+	private static final long serialVersionUID = 1L;
+
+}