chore: update select styles (#39107)

/ok-to-test tags="@tag.Sanity"

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> Workflow run:
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> Commit: 47f2f8d146ce02972c033d6b727f6490d13d891c
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> Tags: `@tag.Sanity`
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> <hr>Fri, 07 Feb 2025 09:05:25 UTC
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<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **Style**
- Refined the appearance of selection options to ensure clear visual
feedback.
- Updated the search input border styling for a more consistent and
polished look during user interactions.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

app/client/packages/design-system/ads/src/Select/styles.css

@@ -341,8 +341,11 @@
 }
 
 /* selected */
+/* if the option is selected and does not have a checkbox ( identified by label ), then we need to add a background color */
 .ads-v2-select__dropdown
-  .rc-select-item.rc-select-item-option.rc-select-item-option-selected {
+  .rc-select-item.rc-select-item-option.rc-select-item-option-selected:not(
+    :has(label)
+  ) {
   --select-option-color-bg: var(--ads-v2-colors-content-surface-active-bg);
 }
 
@@ -378,7 +381,7 @@
   border-top: none;
   border-left: none;
   border-right: none;
-  border-bottom: 1px solid var(--ads-v2-color-border-emphasis);
+  border-bottom: 1px solid var(--ads-v2-color-border);
   border-radius: 0;
   outline: none !important;
 }