Fix random failure in WordContributionEventDaoTest

[jo-elimu]

The unit test at WordContributionEventDaoTest fails randomly, so it probably has something to do with the random execution order of the tests.

https://github.com/elimu-ai/webapp/actions/runs/7737336544/job/21096137074?pr=1643

[INFO] Tests run: 4, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.047 s - in ai.elimu.web.SignOnControllerWeb3Test
06:47:17.917 [SpringContextShutdownHook] INFO  org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean - Closing JPA EntityManagerFactory for persistence unit 'default'
[INFO] 
[INFO] Results:
[INFO] 
Error:  Failures: 
Error:    WordContributionEventDaoTest.testReadMostRecentPerWord:111 
Expected: is <2>
     but: was <3>
[INFO] 
Error:  Tests run: 122, Failures: 1, Errors: 0, Skipped: 2

---

Relates to #1647

[jo-elimu]

https://github.com/elimu-ai/webapp/actions/runs/7754162700/job/21146934845?pr=1646

09:50:52.[141](https://github.com/elimu-ai/webapp/actions/runs/7754162700/job/21146934845?pr=1646#step:7:142) [main] INFO  ai.elimu.dao.WordContributionEventDaoTest - testReadMostRecentPerWord
09:50:52.141 [main] INFO  ai.elimu.dao.WordContributionEventDaoTest - numberOfWordContributionEventsBefore: 0
09:50:52.157 [main] INFO  ai.elimu.dao.WordContributionEventDaoTest - numberOfWordContributionEventsAfter: 1
09:50:52.172 [main] INFO  ai.elimu.dao.WordContributionEventDaoTest - numberOfWordContributionEventsAfter: 2
09:50:52.188 [main] INFO  ai.elimu.dao.WordContributionEventDaoTest - numberOfWordContributionEventsAfter: 3
09:50:52.188 [main] INFO  ai.elimu.dao.WordContributionEventDaoTest - testReadMostRecent
09:50:52.204 [main] INFO  ai.elimu.dao.WordContributionEventDaoTest - numberOfWordContributionEventsBefore: 3
09:50:52.219 [main] INFO  ai.elimu.dao.WordContributionEventDaoTest - numberOfWordContributionEventsAfter: 4
Error:  Tests run: 2, Failures: 1, Errors: 0, Skipped: 0, Time elapsed: 0.109 s <<< FAILURE! - in ai.elimu.dao.WordContributionEventDaoTest
Error:  testReadMostRecentPerWord(ai.elimu.dao.WordContributionEventDaoTest)  Time elapsed: 0.063 s  <<< FAILURE!
java.lang.AssertionError: 

Expected: is <2>
     but: was <3>
	at ai.elimu.dao.WordContributionEventDaoTest.testReadMostRecentPerWord(WordContributionEventDaoTest.java:122)