[8.15] Hide progress bar on initial load when client prefers reduced …

…motion (#194365) (#194495)

# Backport

This will backport the following commits from `main` to `8.15`:
- [Hide progress bar on initial load when client prefers reduced motion
(#194365)](#194365)

<!--- Backport version: 9.4.3 -->

### Questions ?
Please refer to the [Backport tool
documentation](https:/sqren/backport)

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progress bar on initial load when client prefers reduced motion
(#194365)\n\n##
Summary\r\n\r\nSee\r\nhttps://developer.mozilla.org/en-US/docs/Web/CSS/@media/prefers-reduced-motion\r\n\r\n![CleanShot
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(#194365)\n\n##
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2024-09-29 at 21
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progress bar on initial load when client prefers reduced motion
(#194365)\n\n##
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2024-09-29 at 21
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BACKPORT-->

Co-authored-by: Nathan L Smith <[email protected]>

packages/core/apps/core-apps-server-internal/assets/legacy_styles.css

@@ -114,3 +114,9 @@ body, html {
  transform: scaleX(1) translateX(100%);
  }
 }
+
+@media (prefers-reduced-motion) {
+ .kbnProgress {
+ display: none;
+ }
+}