Bump io.undertow:undertow-core from 2.3.12.Final to 2.3.20.Final

Bumps [io.undertow:undertow-core](https://github.com/undertow-io/undertow) from 2.3.12.Final to 2.3.20.Final.
- [Release notes](https://github.com/undertow-io/undertow/releases)
- [Commits](undertow-io/undertow@2.3.12.Final...2.3.20.Final)

---
updated-dependencies:
- dependency-name: io.undertow:undertow-core
  dependency-version: 2.3.20.Final
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

core/build.gradle.kts

@@ -25,8 +25,8 @@ dependencies {
     compileOnly("org.spongepowered:configurate-yaml:4.2.0")
     compileOnly("org.snakeyaml:snakeyaml-engine:2.10")
     api("org.slf4j:slf4j-api:2.0.17")
-    api("io.undertow:undertow-core:2.3.12.Final")
-    api("io.undertow:undertow-websockets-jsr:2.3.12.Final")
+    api("io.undertow:undertow-core:2.3.20.Final")
+    api("io.undertow:undertow-websockets-jsr:2.3.20.Final")
 
     compileOnly("net.kyori:adventure-text-minimessage:4.17.0")