Bump jackson-databind from 2.10.2 to 2.12.7.1 in /guestbook

Bumps [jackson-databind](https://github.com/FasterXML/jackson) from 2.10.2 to 2.12.7.1.
- [Release notes](https://github.com/FasterXML/jackson/releases)
- [Commits](https://github.com/FasterXML/jackson/commits)

---
updated-dependencies:
- dependency-name: com.fasterxml.jackson.core:jackson-databind
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

guestbook/pom.xml

@@ -10,7 +10,7 @@
   <properties>
   	<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
   	<spring.version>4.3.5.RELEASE</spring.version>
-  	<jackson2.version> 2.10.2</jackson2.version>
+  	<jackson2.version>2.12.7.1</jackson2.version>
   </properties>
 
   <dependencies>