Update Gradle wrapper to 5.6.2
Update Gradle wrapper to 5.6.2

Update Gradle distribution version & regenerate wrapper to pick up recent changes per
https://docs.gradle.org/current/userguide/gradle_wrapper.html#sec:upgrading_wrapper

    ./gradlew wrapper --gradle-version 5.6.2

Signed-off-by: Roger Sheen <a61a1add71dadc74037ae5e44ee30713db9a7451@infotexture.net>

infotexture/docs,dita-ot/docs,infotexture/docs