Add regression fix changelog entry in 1.7 too

Author: cderv

news/changelog-1.7.md

@@ -7,6 +7,7 @@ All changes included in 1.7:
 - ([#11549](https://github.com/quarto-dev/quarto-cli/issues/11549)): Fix regression in rendering `dashboard` tabsets into cards without titles.
 - ([#11580](https://github.com/quarto-dev/quarto-cli/issues/11580)): Fix regression with documents containing `categories` fields that are not strings.
 - ([#11752](https://github.com/quarto-dev/quarto-cli/issues/11752)): Fix regression with non-alphanumeric characters in `categories` preventing correct filtering of listing.
+- ([#11561](https://github.com/quarto-dev/quarto-cli/issues/11561)): Fix a regression with `$border-color` that impacted, callouts borders, tabset borders, and table borders of the defaults themes. `$border-color` is now correctly a mixed of `$body-color` and `$body-bg` even for the default theme.
 
 ## YAML validation