docs(migration): mention spinners slow down (#31929)

site/content/docs/5.0/migration.md

@@ -15,6 +15,7 @@ toc: true
 - All `lighten()` and `darken()` functions in our codebase are replaced by `tint-color()` and `shade-color()`. These functions will mix the color with either white or black instead of changing its lightness by a fixed amount.
 - The `scale-color()` will either tint or shade a color depending on whether its weight parameter is positive or negative.
 - See [this PR](https://github.com/twbs/bootstrap/pull/30622) for more details.
+- Spinners now honor `prefers-reduced-motion: reduce` by slowing down animations. [See #31882](https://github.com/twbs/bootstrap/pull/31882).
 
 ### Reboot