Align with Framework’s removal of charset attribute from application/json

Closes gh-16979

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/cloudfoundry/servlet/CloudFoundryActuatorAutoConfigurationTests.java

@@ -110,9 +110,8 @@ public class CloudFoundryActuatorAutoConfigurationTests {
 						"vcap.application.cf_api:https://my-cloud-controller.com")
 				.run((context) -> {
 					MockMvc mockMvc = MockMvcBuilders.webAppContextSetup(context).build();
-					mockMvc.perform(get("/cloudfoundryapplication"))
-							.andExpect(header().string("Content-Type",
-									ActuatorMediaType.V2_JSON + ";charset=UTF-8"));
+					mockMvc.perform(get("/cloudfoundryapplication")).andExpect(
+							header().string("Content-Type", ActuatorMediaType.V2_JSON));
 				});
 	}
 

spring-boot-project/spring-boot-test-autoconfigure/src/test/java/org/springframework/boot/test/autoconfigure/web/servlet/mockmvc/WebMvcTestHateoasIntegrationTests.java

@@ -44,8 +44,8 @@ public class WebMvcTestHateoasIntegrationTests {
 
 	@Test
 	public void plainResponse() throws Exception {
-		this.mockMvc.perform(get("/hateoas/plain")).andExpect(header()
-				.string(HttpHeaders.CONTENT_TYPE, "application/json;charset=UTF-8"));
+		this.mockMvc.perform(get("/hateoas/plain"))
+				.andExpect(header().string(HttpHeaders.CONTENT_TYPE, "application/json"));
 	}
 
 	@Test

spring-boot-samples/spring-boot-sample-hateoas/src/test/java/sample/hateoas/SampleHateoasApplicationTests.java

@@ -56,7 +56,7 @@ class SampleHateoasApplicationTests {
 				HttpMethod.GET, request, String.class);
 		assertThat(response.getStatusCode()).isEqualTo(HttpStatus.OK);
 		assertThat(response.getHeaders().getContentType())
-				.isEqualTo(MediaType.parseMediaType("application/json;charset=UTF-8"));
+				.isEqualTo(MediaType.parseMediaType("application/json"));
 	}
 
 }