deps: bump me.paulschwarz:spring-dotenv in /samples/java/token-refresh

Bumps [me.paulschwarz:spring-dotenv](https://github.com/paulschwarz/spring-dotenv) from 4.0.0 to 5.1.0.
- [Release notes](https://github.com/paulschwarz/spring-dotenv/releases)
- [Changelog](https://github.com/paulschwarz/spring-dotenv/blob/main/CHANGELOG.md)
- [Commits](paulschwarz/spring-dotenv@v4.0.0...v5.1.0)

---
updated-dependencies:
- dependency-name: me.paulschwarz:spring-dotenv
  dependency-version: 5.1.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

samples/java/token-refresh/pom.xml

@@ -36,7 +36,7 @@
         <dependency>
             <groupId>me.paulschwarz</groupId>
             <artifactId>spring-dotenv</artifactId>
-            <version>4.0.0</version>
+            <version>5.1.0</version>
         </dependency>
 
         <dependency>