styles(explore): Fix spacing between explore toolbar visualize (#83449)

The `+ Add Series` button was too close to the block below so it didn't
look quite right. Add some spacing so it's closer to the block above
where it adds the series to.

Author: Zylphrex

Diff for: static/app/views/explore/toolbar/styles.tsx

@@ -36,7 +36,11 @@ export const ToolbarFooterButton = styled(Button)<{disabled?: boolean}>`
   color: ${p => (p.disabled ? p.theme.gray300 : p.theme.linkColor)};
 `;
 
-export const ToolbarFooter = styled('div')<{disabled?: boolean}>``;
+export const ToolbarFooter = styled('div')<{disabled?: boolean}>`
+  :not(:last-child) {
+    margin-bottom: ${space(0.5)};
+  }
+`;
 
 export const ToolbarRow = styled('div')`
   display: flex;