* chore: Update Gradle to 6.3
* fix: Java 13 ambigiuous method call
According to https://www.oracle.com/technetwork/java/13-relnote-issues-5460548.html#JDK-8218875
the `null` parameter should be cast to `Classloader` to solve this.
* chore(actions): Run with Java 14 in CI
Co-authored-by: Niruandaleth <jd.rueckert@googlemail.com>