Docs: clarify WebView support for cleartext traffic

No change to logic, docs change only.

WebView added support for android:usesCleartextTraffic for apps
targeting O and above (API level 26). This CL clarifies WebView's
support in the Android documentation.

This also fixes a preexisting presubmit error in
NetworkSecurityPolicy.java (unused import).

Bug: 67714197
Test: N/A
Change-Id: If6bfd36bc65926a1b032813598c85146ccfde969
diff --git a/core/java/android/content/pm/ApplicationInfo.java b/core/java/android/content/pm/ApplicationInfo.java
index d73f852..dcc6821 100644
--- a/core/java/android/content/pm/ApplicationInfo.java
+++ b/core/java/android/content/pm/ApplicationInfo.java
@@ -375,7 +375,7 @@
      * {@code DownloadManager}, {@code MediaPlayer}) will refuse app's requests to use cleartext
      * traffic. Third-party libraries are encouraged to honor this flag as well.
      *
-     * <p>NOTE: {@code WebView} does not honor this flag.
+     * <p>NOTE: {@code WebView} honors this flag for applications targeting API level 26 and up.
      *
      * <p>This flag is ignored on Android N and above if an Android Network Security Config is
      * present.