Match shimmer overlay flexShrink to real label row

The shimmerText style forced flexShrink: 1 on the primary label, while
the real label has flexShrink: 0. With long secondary labels, the
shimmer truncated the primary label and shifted the secondary
truncation point, so the shimmer no longer aligned with the actual
text. Drop the override so each shimmer label inherits its base
flexShrink.

packages/app/src/components/message.tsx

@@ -1060,7 +1060,6 @@ const expandableBadgeStylesheet = StyleSheet.create((theme) => ({
     color: "transparent",
     fontSize: theme.fontSize.base,
     fontWeight: theme.fontWeight.normal,
-    flexShrink: 1,
   },
   spacer: {
     flex: 1,