Remove MessageSourceAutoConfigurationIntegrationTests, MessageSourceAutoConfigurationProfileTests, and SpringJUnitTests

[wilkinsona]

All three tests appear to be testing functionality that's tested elsewhere.

• MessageSourceAutoConfigurationIntegrationTests is testing that a configuration property can be set by @SpringBootTest
• MessageSourceAutoConfigurationProfileTests is testing that profile can be activated by @ActiveProfiles and that a profile-specific configuration file is then loaded
• SpringJUnitTests is testing that @Value can resolve placeholders from the environment and that the environment has been populated by `application.properties