Migrate negative margin utils to Tailwind

What does this MR do and why?

Migrates remaining negative margin utils to Tailwind:

• gl-mb-n* -> -gl-mb-*
• gl-ml-n* -> -gl-ml-*

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CSS-in-Js diff

diff --git a/config/helpers/tailwind/css_in_js.js b/config/helpers/tailwind/css_in_js.js
index 397076c0d1cb..51193a80f66c 100644
--- a/config/helpers/tailwind/css_in_js.js
+++ b/config/helpers/tailwind/css_in_js.js
@@ -1,5 +1,5 @@
 /**
- * The following 544 definitions need to be migrated to Tailwind.
+ * The following 535 definitions need to be migrated to Tailwind.
  * Let's do this! 🚀
  */
 module.exports = {
@@ -468,24 +468,15 @@ module.exports = {
   '.sm-mr-3': { '@media (min-width: 576px)': { 'margin-right': '0.5rem' } },
   '.mb-0\\!': { 'margin-bottom': '0 !important' },
   '.mb-1\\!': { 'margin-bottom': '0.125rem !important' },
-  '.mb-n1': { 'margin-bottom': '-0.125rem' },
   '.mb-2\\!': { 'margin-bottom': '0.25rem !important' },
-  '.mb-n2': { 'margin-bottom': '-0.25rem' },
   '.mb-3\\!': { 'margin-bottom': '0.5rem !important' },
-  '.mb-n3': { 'margin-bottom': '-0.5rem' },
-  '.mb-n3\\!': { 'margin-bottom': '-0.5rem !important' },
   '.mb-4\\!': { 'margin-bottom': '0.75rem !important' },
   '.mb-5\\!': { 'margin-bottom': '1rem !important' },
   '.mb-6\\!': { 'margin-bottom': '1.5rem !important' },
   '.sm-ml-auto': { '@media (min-width: 576px)': { 'margin-left': 'auto' } },
   '.ml-0\\!': { 'margin-left': '0 !important' },
-  '.ml-n1': { 'margin-left': '-0.125rem' },
   '.ml-2\\!': { 'margin-left': '0.25rem !important' },
-  '.ml-n2': { 'margin-left': '-0.25rem' },
   '.ml-3\\!': { 'margin-left': '0.5rem !important' },
-  '.ml-n3': { 'margin-left': '-0.5rem' },
-  '.ml-n4': { 'margin-left': '-0.75rem' },
-  '.ml-n4\\!': { 'margin-left': '-0.75rem !important' },
   '.my-0\\!': { 'margin-top': '0 !important', 'margin-bottom': '0 !important' },
   '.my-2\\!': { 'margin-top': '0.25rem !important', 'margin-bottom': '0.25rem !important' },
   '.my-4\\!': { 'margin-top': '0.75rem !important', 'margin-bottom': '0.75rem !important' },

Related to #456630 (closed)