Upgrade to MongoDB 4.4 on CI

[mp911de]

Currently, builds fail with:

11:23:10  [ERROR] org.springframework.data.mongodb.core.MongoTemplateFieldProjectionTests.mapsNestedPathAggregationExpressionToDomainType  Time elapsed: 0.043 s  <<< ERROR!
11:23:10  org.springframework.data.mongodb.UncategorizedMongoDbException: Query failed with error code 2 and error message 'Unsupported projection option: person.last_name: { $toUpper: "$person.last_name" }' on server 127.0.0.1:27017; nested exception is com.mongodb.MongoQueryException: Query failed with error code 2 and error message 'Unsupported projection option: person.last_name: { $toUpper: "$person.last_name" }' on server 127.0.0.1:27017
11:23:10  	at org.springframework.data.mongodb.core.MongoTemplateFieldProjectionTests.mapsNestedPathAggregationExpressionToDomainType(MongoTemplateFieldProjectionTests.java:124)
11:23:10  Caused by: com.mongodb.MongoQueryException: Query failed with error code 2 and error message 'Unsupported projection option: person.last_name: { $toUpper: "$person.last_name" }' on server 127.0.0.1:27017
11:23:10  	at org.springframework.data.mongodb.core.MongoTemplateFieldProjectionTests.mapsNestedPathAggregationExpressionToDomainType(MongoTemplateFieldProjectionTests.java:124)

See https://jenkins.spring.io/view/SpringData/job/spring-data-mongodb/job/master/500/console