Update dependency ca.uhn.hapi.fhir:hapi-fhir-client to v8.6.4

Author: renovate[bot]

pom.xml

@@ -28,7 +28,7 @@
     <dependency>
       <groupId>ca.uhn.hapi.fhir</groupId>
       <artifactId>hapi-fhir-client</artifactId>
-      <version>8.0.0</version>
+      <version>8.6.4</version>
     </dependency>
     <dependency>
       <groupId>ca.uhn.hapi.fhir</groupId>