Fix accept param validation (#138)

Author: gaetano-miglionico

apps/institution-ms/web/src/main/java/it/pagopa/selfcare/mscore/web/controller/InstitutionController.java

@@ -387,7 +387,7 @@ public ResponseEntity<InstitutionResponse> onboardingInstitution(@RequestBody @V
 
     @ResponseStatus(HttpStatus.NO_CONTENT)
     @ApiOperation(value = "${swagger.mscore.onboarding.users.delete}", notes = "${swagger.mscore.onboarding.users.delete}")
-    @DeleteMapping(value = "/{id}/products/{productId}", produces = MediaType.APPLICATION_JSON_VALUE)
+    @DeleteMapping(value = "/{id}/products/{productId}", produces = MediaType.APPLICATION_PROBLEM_JSON_VALUE)
     public void deleteOnboardedInstitution(@PathVariable("productId") String productId,
                                            @PathVariable("id") String institutionId) {