Bump nanohttpd from 2.2.0 to 2.3.1

Bumps [nanohttpd](https://github.com/NanoHttpd/nanohttpd) from 2.2.0 to 2.3.1.
- [Release notes](https://github.com/NanoHttpd/nanohttpd/releases)
- [Changelog](https://github.com/NanoHttpd/nanohttpd/blob/master/nanohttpd%20release%20perform.launch)
- [Commits](NanoHttpd/nanohttpd@nanohttpd-project-2.2.0...nanohttpd-project-2.3.1)

Signed-off-by: dependabot[bot] <support@github.com>

pom.xml

@@ -58,7 +58,7 @@
     <dependency>
       <groupId>org.nanohttpd</groupId>
       <artifactId>nanohttpd</artifactId>
-      <version>2.2.0</version>
+      <version>2.3.1</version>
       <scope>test</scope>
     </dependency>
   </dependencies>