Bump com.github.jnr:jnr-posix from 3.1.18 to 3.1.20

Bumps [com.github.jnr:jnr-posix](https://github.com/jnr/jnr-posix) from 3.1.18 to 3.1.20.
- [Commits](jnr/jnr-posix@jnr-posix-3.1.18...jnr-posix-3.1.20)

---
updated-dependencies:
- dependency-name: com.github.jnr:jnr-posix
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

grails-shell/build.gradle

@@ -38,7 +38,7 @@ dependencies {
     implementation("commons-codec:commons-codec:1.16.1")
 
     testImplementation "net.sf.expectit:expectit-core:0.9.0"
-    testImplementation "com.github.jnr:jnr-posix:3.1.18"
+    testImplementation "com.github.jnr:jnr-posix:3.1.20"
 
     runtimeOnly "org.slf4j:slf4j-simple:$slf4jVersion"
     runtimeOnly "org.codehaus.plexus:plexus-component-api:1.0-alpha-33"