Migrate `gl-white-space-nowrap` to Tailwind equivalent

What does this MR do and why?

Related to #456634, #456616, #456589

The CSS utils task group is in the process of migrating legacy CSS utilities to the Tailwind equivalent. This MR migrates the gl-white-space-nowrap legacy utils to the Tailwind equivalent. Tailwind uses whitespace (without a dash between white and space) where-as our legacy utils use white-space. Did a bit of digging and it looks like Tailwind decided to use this naming because whitespace is typically one word (see https://github.com/tailwindlabs/tailwindcss/issues/776#issuecomment-474104838)

For anyone curious, it's because "whitespace" (no hyphen) is the proper term, according to Wikipedia at least: https://en.wikipedia.org/wiki/Whitespace_character

I kind of wish they had stuck with the CSS naming but also I can never remember which way it is in vanilla CSS so it doesn't really matter 😆

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gl-white-space-nowrap is used in GitLab UI so that one won't be removed from css_in_js.js until we migrate it in GitLab UI

--- a/config/helpers/tailwind/css_in_js.js
+++ b/config/helpers/tailwind/css_in_js.js
@@ -1,5 +1,5 @@
 /**
- * The following 609 definitions need to be migrated to Tailwind.
+ * The following 607 definitions need to be migrated to Tailwind.
  * Let's do this! 🚀
  */
 module.exports = {
@@ -655,11 +655,9 @@ module.exports = {
   '.white-space-normal': { 'white-space': 'normal' },
   '.white-space-normal\\!': { 'white-space': 'normal !important' },
   '.white-space-nowrap': { 'white-space': 'nowrap' },
-  '.white-space-nowrap\\!': { 'white-space': 'nowrap !important' },
   '.white-space-pre-wrap': { 'white-space': 'pre-wrap' },
   '.white-space-pre-wrap\\!': { 'white-space': 'pre-wrap !important' },
   '.white-space-pre-line': { 'white-space': 'pre-line' },
-  '.md-white-space-nowrap': { '@media (min-width: 768px)': { 'white-space': 'nowrap' } },
   '.word-break-all': { 'word-break': 'break-all' },
   '.word-break-all\\!': { 'word-break': 'break-all !important' },
   '.word-break-word': { 'word-break': 'break-word' },

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