Fix TalkBack crash in CardInputWidget

**Summary**
`android:accessibilityTraversalAfter` on both
the expiration date and CVC input views were
pointing to the wrong views.

**Testing**
On a Google Pixel, confirmed that TalkBack is
no longer crashing when navigating through
the input views of CardInputWidget.

**Motivation**
Fixes #682

stripe/res/layout/card_input_widget.xml

@@ -83,8 +83,8 @@
             android:hint="@string/expiry_date_hint"
             tools:ignore="UnusedAttribute"
             tools:importantForAccessibility="yes"
-            android:accessibilityTraversalAfter="@+id/et_expiry_date"
             android:accessibilityTraversalBefore="@id/et_card_number"
+            android:accessibilityTraversalAfter="@+id/et_cvc_number"
             android:nextFocusRight="@+id/et_cvc_number"
             android:nextFocusForward="@+id/et_cvc_number"
             android:nextFocusDown="@+id/et_cvc_number"
@@ -107,7 +107,6 @@
             android:layout_height="wrap_content"
             tools:ignore="UnusedAttribute"
             tools:importantForAccessibility="yes"
-            android:accessibilityTraversalAfter="@+id/et_expiry_date"
             android:nextFocusLeft="@id/et_expiry_date"
             android:nextFocusUp="@id/et_expiry_date"
             android:background="@android:color/transparent"