Remove MediaType.APPLICTION_JSON_UTF8 Usage

[rwinch]

Spring Framework removed MediaType.APPLICTION_JSON_UTF8 as a part of 5044b70a4038f2ae29cee262f63fb0e940297bda for spring-projects/spring-framework#33809

For now we will create MediaTypes.APPLICTION_JSON_UTF8 to allow the removal on Spring Framework. We will need to separately revisit this to have it removed in