Adopt to changed Mockk artifact name.

Closes #4161

spring-data-mongodb/pom.xml

@@ -304,7 +304,7 @@
 
 		<dependency>
 			<groupId>io.mockk</groupId>
-			<artifactId>mockk</artifactId>
+			<artifactId>mockk-jvm</artifactId>
 			<version>${mockk}</version>
 			<scope>test</scope>
 		</dependency>

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/MongoTemplateUnitTests.java

@@ -2458,8 +2458,7 @@ public class MongoTemplateUnitTests extends MongoOperationsUnitTests {
 
 	@Override
 	protected MongoOperations getOperationsForExceptionHandling() {
-		MongoTemplate template = spy(this.template);
-		lenient().when(template.getDb()).thenThrow(new MongoException("Error"));
+		when(template.getMongoDatabaseFactory().getMongoDatabase()).thenThrow(new MongoException("Error"));
 		return template;
 	}