Update setUserAgentString API description

As we support override the uesr-agent metadata, updating setUserAgentString API description to line up the latest changes.

Change-Id: I3e8b3affd0b2f3e00a96060c1abee8efd8763e90
diff --git a/core/java/android/webkit/WebSettings.java b/core/java/android/webkit/WebSettings.java
index 3160057..14c5348 100644
--- a/core/java/android/webkit/WebSettings.java
+++ b/core/java/android/webkit/WebSettings.java
@@ -1367,7 +1367,10 @@
      * the system default value will be used.
      *
      * <p>If the user-agent is overridden in this way, the values of the User-Agent Client Hints
-     * headers and {@code navigator.userAgentData} for this WebView will be empty.
+     * headers and {@code navigator.userAgentData} for this WebView could be changed.
+     * <p> See <a href="{@docRoot}reference/androidx/webkit/WebSettingsCompat
+     * #setUserAgentMetadata(WebSettings,UserAgentMetadata)">androidx.webkit.WebSettingsCompat
+     * #setUserAgentMetadata(WebSettings,UserAgentMetadata)</a> for details.
      *
      * <p>Note that starting from {@link android.os.Build.VERSION_CODES#KITKAT} Android
      * version, changing the user-agent while loading a web page causes WebView