fix: pom.xml to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JAVA-CAUHNHAPIFHIR-8344146
- https://snyk.io/vuln/SNYK-JAVA-CAUHNHAPIFHIR-8344149
- https://snyk.io/vuln/SNYK-JAVA-CAUHNHAPIFHIR-7924769
- https://snyk.io/vuln/SNYK-JAVA-CAUHNHAPIFHIR-7924772
- https://snyk.io/vuln/SNYK-JAVA-CAUHNHAPIFHIR-8366323
- https://snyk.io/vuln/SNYK-JAVA-CAUHNHAPIFHIR-8366327
- https://snyk.io/vuln/SNYK-JAVA-COMMONSIO-8161190
- https://snyk.io/vuln/SNYK-JAVA-COMGOOGLEGUAVA-5710356

pom.xml

@@ -109,7 +109,7 @@
         <dependency>
             <groupId>ca.uhn.hapi.fhir</groupId>
             <artifactId>hapi-fhir-structures-r4</artifactId>
-            <version>6.6.2</version>
+            <version>7.6.0</version>
         </dependency>
 
         <dependency>