fix: pom.xml & jackson-jaxb/pom.xml to reduce vulnerabilities (OpenFeign#975)

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JAVA-COMFASTERXMLJACKSONCORE-174736

Author: snyk-bot

jackson-jaxb/pom.xml

@@ -52,7 +52,7 @@
     <dependency>
       <groupId>com.fasterxml.jackson.jaxrs</groupId>
       <artifactId>jackson-jaxrs-json-provider</artifactId>
-      <version>2.6.4</version>
+      <version>2.9.9</version>
     </dependency>
 
     <!-- RuntimeDelegateImpl -->

pom.xml

@@ -72,7 +72,7 @@
     <bouncy.version>1.60</bouncy.version>
 
     <junit.version>4.12</junit.version>
-    <jackson.version>2.9.8</jackson.version>
+    <jackson.version>2.9.9</jackson.version>
     <assertj.version>3.10.0</assertj.version>
 
     <animal-sniffer-maven-plugin.version>1.17</animal-sniffer-maven-plugin.version>