CloseGuard: Fix JavaDoc code sample to use correct API

The code sample in the JavaDoc shows
`CloseGuard.get()` to create a new CloseGuard,
which is incorrect.
The correct API is `new CloseGuard()`.

Bug: 148291235
Test: compiles
Change-Id: I1dd24fff150e671007b67c023b20e078557f2966
diff --git a/core/java/android/util/CloseGuard.java b/core/java/android/util/CloseGuard.java
index 6ac7696..ba504a3 100644
--- a/core/java/android/util/CloseGuard.java
+++ b/core/java/android/util/CloseGuard.java
@@ -26,7 +26,7 @@
  * A simple example: <pre>   {@code
  *   class Foo {
  *
- *       private final CloseGuard guard = CloseGuard.get();
+ *       private final CloseGuard guard = new CloseGuard();
  *
  *       ...
  *
@@ -64,7 +64,7 @@
  * be deferred. For example: <pre>   {@code
  *   class Bar {
  *
- *       private final CloseGuard guard = CloseGuard.get();
+ *       private final CloseGuard guard = new CloseGuard();
  *
  *       ...
  *