[Java Runtime Sandbox] fix: unable to set preferred IPv4 property

app/src/main/java/net/kdt/pojavlaunch/Tools.java

@@ -79,7 +79,7 @@ public final class Tools
         List<String> overrideableArgList = new ArrayList<String>();
 
         overrideableArgList.add("-Djava.security.manager");
-        overrideableArgList.add("-Djava.security.policy=java_sandbox.policy");
+        overrideableArgList.add("-Djava.security.policy==java_sandbox.policy");
         
         overrideableArgList.add("-Djava.home=" + Tools.DIR_HOME_JRE);
         overrideableArgList.add("-Djava.io.tmpdir=" + ctx.getCacheDir().getAbsolutePath());