Remove style that breaks pre-L builds and isn't necessary anyway

BUG=470661

Review URL: https://codereview.chromium.org/1033003004

Cr-Commit-Position: refs/heads/master@{#322465}

chrome/android/java/res/layout/autofill_card_unmask_prompt.xml

@@ -176,7 +176,6 @@
             android:id="@+id/verification_progress_bar"
             android:layout_width="16dp"
             android:layout_height="16dp"
-            style="@android:style/Widget.Material.Light.ProgressBar.Small"
             android:visibility="gone" />
 
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