chore: tune jvm build args (#614)

Seem to be running out of metaspace generating API docs.

`MaxPermSize` is supposedly a deprecated JVM argument as of 1.8 (replaced by metaspace) so I have removed that and doubled the metaspace.

Author: aajtodd

gradle.properties

@@ -3,7 +3,7 @@ kotlin.mpp.stability.nowarn=true
 kotlin.native.ignoreDisabledTargets=true
 
 # gradle
-org.gradle.jvmargs=-Xmx6g -XX:MaxPermSize=6g -XX:MaxMetaspaceSize=1G
+org.gradle.jvmargs=-Xmx6g -XX:MaxMetaspaceSize=2G
 
 # sdk
 sdkVersion=0.16.0-SNAPSHOT