fix: pom.xml to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JAVA-COMFASTERXMLJACKSONCORE-15365924

Author: snyk-bot

pom.xml

@@ -152,7 +152,7 @@
         <dependency>
             <groupId>com.fasterxml.jackson.datatype</groupId>
             <artifactId>jackson-datatype-jdk8</artifactId>
-            <version>2.8.6</version>
+            <version>2.18.6</version>
         </dependency>
         <dependency>
             <groupId>org.asynchttpclient</groupId>
@@ -167,22 +167,22 @@
         <dependency>
             <groupId>com.fasterxml.jackson.datatype</groupId>
             <artifactId>jackson-datatype-guava</artifactId>
-            <version>2.9.5</version>
+            <version>2.18.6</version>
         </dependency>
         <dependency>
             <groupId>com.fasterxml.jackson.dataformat</groupId>
             <artifactId>jackson-dataformat-xml</artifactId>
-            <version>2.9.4</version>
+            <version>2.18.6</version>
         </dependency>
         <dependency>
             <groupId>com.fasterxml.jackson.core</groupId>
             <artifactId>jackson-core</artifactId>
-            <version>2.9.5</version>
+            <version>2.18.6</version>
         </dependency>
         <dependency>
             <groupId>com.fasterxml.jackson.core</groupId>
             <artifactId>jackson-databind</artifactId>
-            <version>2.9.5</version>
+            <version>2.18.6</version>
         </dependency>
         <dependency>
             <groupId>org.assertj</groupId>