Bump spring-webmvc from 5.3.17 to 5.3.18 in /json-unit-spring

Bumps [spring-webmvc](https://github.com/spring-projects/spring-framework) from 5.3.17 to 5.3.18.
- [Release notes](https://github.com/spring-projects/spring-framework/releases)
- [Commits](spring-projects/spring-framework@v5.3.17...v5.3.18)

---
updated-dependencies:
- dependency-name: org.springframework:spring-webmvc
  dependency-type: direct:development
...

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

json-unit-spring/pom.xml

@@ -6,7 +6,7 @@
         Spring Mock assertions
     </description>
     <properties>
-        <spring.version>5.3.17</spring.version>
+        <spring.version>5.3.18</spring.version>
         <kotlin.compiler.jvmTarget>1.8</kotlin.compiler.jvmTarget>
         <osgi.exportPackage>net.javacrumbs.jsonunit.spring</osgi.exportPackage>
     </properties>