Update btn-close-white docs to filter (not backdrop-filter) (#31796)

This PR fixes an error in the v5 docs. The btn-close-white class actually uses the filter (not backdrop-filter)

site/content/docs/5.0/components/close-button.md

@@ -24,7 +24,7 @@ Disabled close buttons change their `opacity`. We've also applied `pointer-event
 
 ## White variant
 
-Change the default `.btn-close` to be white with the `.btn-close-white` class. This class uses the `backdrop-filter` property to invert the `background-image`.
+Change the default `.btn-close` to be white with the `.btn-close-white` class. This class uses the `filter` property to invert the `background-image`.
 
 {{< example class="bg-dark" >}}
 <button type="button" class="btn-close btn-close-white" aria-label="Close"></button>

site/content/docs/5.0/migration.md

@@ -65,7 +65,7 @@ toc: true
 - Renamed `.close` to `.btn-close` for a less generic name.
 - Close buttons now use a `background-image` (embedded SVG) instead of a `×` in the HTML, allowing for easier customization without the need to touch your markup.
 - Added new variables to better control the customization.
-- Added new `.btn-close-white` variant that uses `backdrop-filter: invert(1)` to enable higher contrast dismiss icons against darker backgrounds.
+- Added new `.btn-close-white` variant that uses `filter: invert(1)` to enable higher contrast dismiss icons against darker backgrounds.
 
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