Fix spacing issue due to Tailwind conflict

What does this MR do and why?

I noticed a minor issue due to a conflict between our legacy CSS utility classes and Tailwind utility classes. There are a few places where we use gl-gap-x-* or gl-gap-y-*. In these look like:

'.gap-x-3 > * + *': { 'margin-left': '0.5rem' },
'.gap-x-5 > * + *': { 'margin-left': '1rem' },
'.gap-y-3 > * + *': { 'margin-top': '0.5rem' },

But in Tailwind these utilities use column-gap or row-gap. This means if the element also has display: flex then there is duplicate gap. Here's how we will fix this:

1. Migrate these to the legacy util gl-column-gap-* except for !150608 (comment 1877941280) (this MR)
2. Remove them from src/scss/utility-mixins/spacing.scss#L867
3. Migrate all the gl-column-gap-* utilities to gl-gap-x-*

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css_in_js.js diff

diff --git a/config/helpers/tailwind/css_in_js.js b/config/helpers/tailwind/css_in_js.js
index 8f7e7c943a4b..1b82df306809 100644
--- a/config/helpers/tailwind/css_in_js.js
+++ b/config/helpers/tailwind/css_in_js.js
@@ -1,5 +1,5 @@
 /**
- * The following 632 definitions need to be migrated to Tailwind.
+ * The following 629 definitions need to be migrated to Tailwind.
  * Let's do this! 🚀
  */
 module.exports = {
@@ -574,9 +574,6 @@ module.exports = {
   '.my-n4': { 'margin-top': '-0.75rem', 'margin-bottom': '-0.75rem' },
   '.mx-n4': { 'margin-left': '-0.75rem', 'margin-right': '-0.75rem' },
   '.mx-n5': { 'margin-left': '-1rem', 'margin-right': '-1rem' },
-  '.gap-x-3 > * + *': { 'margin-left': '0.5rem' },
-  '.gap-x-5 > * + *': { 'margin-left': '1rem' },
-  '.gap-y-3 > * + *': { 'margin-top': '0.5rem' },
   '.sm-gap-3': { '@media (min-width: 576px)': { gap: '0.5rem' } },
   '.column-gap-2': { 'column-gap': '0.25rem' },
   '.column-gap-3': { 'column-gap': '0.5rem' },

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