Bump jackson-databind-nullable from 0.2.3 to 0.2.4 in /api-first-server (#27)

Bumps [jackson-databind-nullable](https://github.com/OpenAPITools/jackson-databind-nullable) from 0.2.3 to 0.2.4.
- [Release notes](https://github.com/OpenAPITools/jackson-databind-nullable/releases)
- [Commits](OpenAPITools/jackson-databind-nullable@v0.2.3...v0.2.4)

---
updated-dependencies:
- dependency-name: org.openapitools:jackson-databind-nullable
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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Author: dependabot[bot]

api-first-server/pom.xml

@@ -18,7 +18,7 @@
         <java.version>11</java.version>
         <swagger-annotations-version>2.2.2</swagger-annotations-version>
         <springfox-version>3.0.0</springfox-version>
-        <jackson-databind-nullable>0.2.3</jackson-databind-nullable>
+        <jackson-databind-nullable>0.2.4</jackson-databind-nullable>
     </properties>
 
     <dependencies>