Fix the until-build property of the IntelliJ plugin.

Setting it to "" creates a broken plugin, but omitting it sets it to the same as
since-build. So apparently you have to do this.

PiperOrigin-RevId: 665927556

idea_plugin/build.gradle.kts

@@ -42,6 +42,7 @@ intellijPlatform {
     version = "${googleJavaFormatVersion}.0"
     ideaVersion {
       sinceBuild = "223"
+      untilBuild = provider { null }
     }
   }