v5: Drop remaining deprecated mixins (#28461)

- Deletes mixin mentions from float docs
- Deletes mixin mention from visibility docs
- Deletes the image-replacement page for text-hide

scss/_mixins.scss

@@ -16,9 +16,7 @@
 @import "mixins/screen-reader";
 @import "mixins/reset-text";
 @import "mixins/text-emphasis";
-@import "mixins/text-hide";
 @import "mixins/text-truncate";
-@import "mixins/visibility";
 
 // // Components
 @import "mixins/alert";
@@ -42,4 +40,3 @@
 @import "mixins/clearfix";
 @import "mixins/grid-framework";
 @import "mixins/grid";
-@import "mixins/float";