Fix fractional values not being parsed properly inside arbitrary properties (#9705)

* remove redundant closing bracket in regex pattern

* test fractional spacing values in theme function

* add test that ensures arbitrary properties are separate

* update changelog

Co-authored-by: Robin Malfait <malfait.robin@gmail.com>

src/lib/defaultExtractor.js

@@ -29,7 +29,7 @@ function* buildRegExps(context) {
 
   let utility = regex.any([
     // Arbitrary properties
-    /\[[^\s:'"`]+:[^\s\]]+\]/,
+    /\[[^\s:'"`]+:[^\s]+\]/,
 
     // Utilities
     regex.pattern([