fix: pom.xml to reduce vulnerabilities (#859)

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JAVA-COMFASTERXMLJACKSONCORE-72448
- https://snyk.io/vuln/SNYK-JAVA-COMFASTERXMLJACKSONCORE-72449
- https://snyk.io/vuln/SNYK-JAVA-COMFASTERXMLJACKSONCORE-72450
- https://snyk.io/vuln/SNYK-JAVA-COMFASTERXMLJACKSONCORE-72451

pom.xml

@@ -70,7 +70,7 @@
     <gson.version>2.5</gson.version>
 
     <junit.version>4.12</junit.version>
-    <jackson.version>2.9.6</jackson.version>
+    <jackson.version>2.9.7</jackson.version>
     <assertj.version>3.10.0</assertj.version>
 
     <animal-sniffer-maven-plugin.version>1.17</animal-sniffer-maven-plugin.version>