Add comment explaining the -3 margin on searchBulkActionsButton

The filter bar row is 34px and the larger button is 40px, so we
offset by half the difference ((40-34)/2 = 3) to prevent layout shift.

Co-authored-by: Shawn Borton <shawnborton@users.noreply.github.com>

Author: MelvinBot

src/styles/index.ts

@@ -4900,6 +4900,8 @@ const staticStyles = (theme: ThemeColors) =>
             minHeight: variables.componentSizeSmall,
         },
 
+        // The filter bar row is 34px tall, but the default (larger) bulk-action button is 40px.
+        // To keep the bar from growing, we pull the button up/down by half the difference: (40 - 34) / 2 = 3.
         searchBulkActionsButton: {
             marginVertical: -3,
         },