Bump org.springframework:spring-web in /tests/sample-apps/echo

Bumps [org.springframework:spring-web](https://github.com/spring-projects/spring-framework) from 6.0.0 to 6.0.18.
- [Release notes](https://github.com/spring-projects/spring-framework/releases)
- [Commits](spring-projects/spring-framework@v6.0.0...v6.0.18)

---
updated-dependencies:
- dependency-name: org.springframework:spring-web
  dependency-type: direct:production
...

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

tests/sample-apps/echo/pom.xml

@@ -14,7 +14,7 @@
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <java.version>1.8</java.version>
         <resteasy.version>3.1.4.Final</resteasy.version>
-        <spring.version>6.0.0</spring.version>
+        <spring.version>6.0.18</spring.version>
     </properties>
 
     <dependencies>