Delete a fix For Ctrl+Backspace in an empty TextField as it's obsolete (

#1653)

The fix #329
is obsolete. It's implemented in the upstream repository:
https://android-review.googlesource.com/c/platform/frameworks/support/+/2425401

We delete this fix made in our fork to reduce the diff between our
repositories.

___

The previously added tests for the fixed bug still pass:
https://github.com/JetBrains/compose-multiplatform-core/blob/1ec1b58c0662d4874b7294f13a79a2e34105d047/compose/foundation/foundation/src/desktopTest/kotlin/androidx/compose/foundation/text/selection/TextSelectionTests.kt#L256

compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/text/selection/TextPreparedSelection.kt

@@ -325,7 +325,6 @@ internal abstract class BaseTextPreparedSelection<T : BaseTextPreparedSelection<
     }
 
     private fun charOffset(offset: Int) = offset.coerceAtMost(text.length - 1)
-            .coerceAtLeast(0)
 
     companion object {
         /**