Add bottom padding to 'Choose a new lock screen'

* Add 24dp padding

Before: https://screenshot.googleplex.com/64sTaMhwqMKQ4CE
After: https://screenshot.googleplex.com/As33LmkLXG7duV5

Bug: 192541032
Test: manual testing (see screenshots)
Change-Id: I4e29e4f776e7be1c42301c39c4844d7ee948eaaa
diff --git a/res/values/styles.xml b/res/values/styles.xml
index 63ea86e..e25c7fa 100644
--- a/res/values/styles.xml
+++ b/res/values/styles.xml
@@ -394,6 +394,7 @@
 
     <style name="BiometricHeaderStyle" parent="@*android:style/TextAppearance.DeviceDefault.Subhead">
         <item name="android:paddingTop">16dp</item>
+        <item name="android:paddingBottom">24dp</item>
         <item name="android:lineSpacingMultiplier">1.2</item>
     </style>