Remove workaround for Bintray publishing (#408)

Bintray no longer exists, so the workaround specified in
gradle/gradle#11412
is no longer applicable.

Author: Goooler

gradle.properties

@@ -20,9 +20,5 @@ kotlin.native.ignoreIncorrectDependencies=true
 kotlin.native.ignoreDisabledTargets=true
 kotlin.mpp.applyDefaultHierarchyTemplate=false
 
-# Workaround for Bintray treating .sha512 files as artifacts
-# https://github.com/gradle/gradle/issues/11412
-systemProp.org.gradle.internal.publish.checksums.insecure=true
-
 # stop using pre-HMPP IDEA import workaround in kotlinx.team.infra
 useNativeBuildInfraInIdea=true