chore(side-panel): fix margin flashing bug (#4378)

Author: nkrantz

.changeset/red-waves-flash.md

@@ -0,0 +1,6 @@
+---
+"@twilio-paste/side-panel": patch
+"@twilio-paste/core": patch
+---
+
+[Side Panel] Fix bug where rendering side panel closed would flash a right margin while breakpointindex was undefined.

packages/paste-core/components/side-panel/src/SidePanelPushContentWrapper.tsx

@@ -34,7 +34,7 @@ export const SidePanelPushContentWrapper = React.forwardRef<HTMLDivElement, Side
         {...safelySpreadBoxProps(props)}
         ref={ref}
         // when using side panels in responsive layouts, we don't want any left margin in small screen, or initial SSR render situations. So basically never apply it in those situations
-        style={breakpointIndex === undefined || breakpointIndex === 0 ? undefined : styles}
+        style={breakpointIndex === 0 ? undefined : styles}
         marginRight={["space0", theme.sizes.size40]}
         minWidth="size0"
         element={element}