[HTMLViewer] Explicitly set WebSettings#setAllowFileAccess to true

WebSettings#setAllowFileAccess default value is changing to be off by
default for Apps targetting API >= 30. This explicitly turns on this
setting for the HTMLViewer app so it can load local files.

Bug: 148840827
Test: N/A
Change-Id: I632cec2af75e90d097e86081a6379afdbdf66162
(cherry picked from commit 57ab31bd6df1dda5c502cef163cb5a7ae3abe71f)

src/com/android/htmlviewer/HTMLViewerActivity.java

diff --git a/src/com/android/htmlviewer/HTMLViewerActivity.java b/src/com/android/htmlviewer/HTMLViewerActivity.java
index 85a16aa..1aa1f68 100644
--- a/src/com/android/htmlviewer/HTMLViewerActivity.java
+++ b/src/com/android/htmlviewer/HTMLViewerActivity.java
@@ -71,6 +71,7 @@
         s.setSavePassword(false);
         s.setSaveFormData(false);
         s.setBlockNetworkLoads(true);
+        s.setAllowFileAccess(true);
 
         // Javascript is purposely disabled, so that nothing can be
         // automatically run.