jni: move package documentation to the package declaration

Updates tailscale/tailscale#1195

Signed-off-by: Elias Naur <mail@eliasnaur.com>

jni/jni.go

@@ -2,10 +2,9 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package jni
-
 // Package jni implements various helper functions for communicating with the Android JVM
 // though JNI.
+package jni
 
 import (
 	"errors"