Bump io.undertow:undertow-core from 2.3.15.Final to 2.3.18.Final

Bumps [io.undertow:undertow-core](https://github.com/undertow-io/undertow) from 2.3.15.Final to 2.3.18.Final.
- [Release notes](https://github.com/undertow-io/undertow/releases)
- [Commits](undertow-io/undertow@2.3.15.Final...2.3.18.Final)

---
updated-dependencies:
- dependency-name: io.undertow:undertow-core
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

pom.xml

@@ -80,7 +80,7 @@
     <jboss-logging-processor.version>2.2.1.Final</jboss-logging-processor.version>
     <jboss.xb.version>2.0.3.GA</jboss.xb.version>
     <jaxws-undertow-httpspi.version>2.0.0.Final</jaxws-undertow-httpspi.version>
-    <io.undertow.version>2.3.15.Final</io.undertow.version>
+    <io.undertow.version>2.3.18.Final</io.undertow.version>
     <jaxb.impl.version>4.0.1</jaxb.impl.version>
     <jboss.jaxbintros.version>2.0.1</jboss.jaxbintros.version>
     <commons-beanutils.version>1.9.4</commons-beanutils.version>