Update the corner radius of bottom sheet

Bug: 191388121
Test: Visually check
Change-Id: I804c8b2aeec4374d2cea13d4876486edec0ec8f6
diff --git a/res/values/dimens.xml b/res/values/dimens.xml
index 1b773ba..09fe893 100755
--- a/res/values/dimens.xml
+++ b/res/values/dimens.xml
@@ -126,7 +126,7 @@
 
     <!-- Dimensions for the "disabled by admin" UI in desktop mode. -->
     <dimen name="disabled_by_admin_desktop_message_text_size">13sp</dimen>
-    <dimen name="preview_bottom_sheet_corner_radius">?android:attr/dialogCornerRadius</dimen>
+    <dimen name="preview_bottom_sheet_corner_radius">12dp</dimen>
 
     <!-- Dimensions for PreviewPager and PageIndicator. -->
     <dimen name="preview_indicator_width">16dp</dimen>