fix normalizing subtraction followed by a variable

[sibbng]

Fixes #9832

-/(-?\d*\.?\d(?!\b-.+[,)](?![^+\-/*])\D)(?:%|[a-z]+)?|\))([+\-/*])/g
+/(-?\d*\.?\d(?!\b-\d.+[,)](?![^+\-/*])\D)(?:%|[a-z]+)?|\))([+\-/*])/g
                   ^ added `\d` to regex

This is fixed the issue but caused some false positives on classes like calc(var(--headings-h1-size)*100):

// normalize-data-types.test.js
-calc(var(--headings-h1-size)*100)
+calc(var(--headings-h1 - size) * 100)

I couldn't figure out how to fix that with regex. To solve this problem, I extracted the variable names and replaced them with safe ones before processing.

[thecrypticace]

Hah, clever fix! I spent some time trying to fix the regex but couldn't come up with one. Thanks!