Bump org.mnode.ical4j:ical4j from 4.0.5 to 4.0.6

Bumps [org.mnode.ical4j:ical4j](https://github.com/ical4j/ical4j) from 4.0.5 to 4.0.6.
- [Release notes](https://github.com/ical4j/ical4j/releases)
- [Changelog](https://github.com/ical4j/ical4j/blob/develop/CHANGELOG.md)
- [Commits](ical4j/ical4j@ical4j-4.0.5...ical4j-4.0.6)

---
updated-dependencies:
- dependency-name: org.mnode.ical4j:ical4j
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

biz.ganttproject.impex.ical/build.gradle

@@ -10,7 +10,7 @@ dependencies {
     providedCompile project(':biz.ganttproject.app.libs')
     providedCompile project(':biz.ganttproject.core')
     providedCompile project(':ganttproject')
-    implementation 'org.mnode.ical4j:ical4j:4.0.5'
+    implementation 'org.mnode.ical4j:ical4j:4.0.6'
 
     testImplementation 'org.junit.jupiter:junit-jupiter-api:5.11.3'
     testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.11.3'