Docs: Update about Safari's support flexbox gap

This callout was added a while ago and Safari has supported this for a while. so lets update the wording.

site/content/docs/5.3/helpers/stacks.md

@@ -11,7 +11,7 @@ added:
 Stacks offer a shortcut for applying a number of flexbox properties to quickly and easily create layouts in Bootstrap. All credit for the concept and implementation goes to the open source [Pylon project](https://almonk.github.io/pylon/).
 
 {{< callout warning >}}
-**Heads up!** Support for gap utilities with flexbox was recently added to Safari, so consider verifying your intended browser support. Grid layout should have no issues. [Read more](https://caniuse.com/flexbox-gap).
+**Heads up!** Support for gap utilities with flexbox isn't available in Safari prior to 14.5, so consider verifying your intended browser support. Grid layout should have no issues. [Read more](https://caniuse.com/flexbox-gap).
 {{< /callout >}}
 
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