Update JAVA_VALIDATOR_VERSION to 6.6.1

Author: github-actions[bot]

action.yml

@@ -45,7 +45,7 @@ inputs:
     required: true
   JAVA_VALIDATOR_VERSION:
     description: 'Version of org.hl7.fhir.core library used for Java-based validation'
-    default: '6.6.0'
+    default: '6.6.1'
     required: true
   JAVA_VALIDATOR_DOWNLOAD_LOCATION:
     description: 'URL from which to download the Java validator JAR'