Revert insertText breaking change that deletes fragment (fixes #5153) (#5154)

This reverts commit 7499d4b4c0.

The issue reported at https://github.com/ianstormtaylor/slate/issues/4862
is a valid complaint, but change in https://github.com/ianstormtaylor/slate/pull/4868
is not an appropriate fix. It is a serious breaking change,
reported as bug: https://github.com/ianstormtaylor/slate/issues/5153

We should therefore revert the change. If we wish to fix Chromium's
triple-click bug, we should do so by unhanging the selection when it is
created; not by changing insertText behavior.

packages/slate-react/src/components/editable.tsx

@@ -648,13 +648,6 @@ export const Editable = (props: EditableProps) => {
           case 'insertFromYank':
           case 'insertReplacementText':
           case 'insertText': {
-            const { selection } = editor
-            if (selection) {
-              if (Range.isExpanded(selection)) {
-                Editor.deleteFragment(editor)
-              }
-            }
-
             if (type === 'insertFromComposition') {
               // COMPAT: in Safari, `compositionend` is dispatched after the
               // `beforeinput` for "insertFromComposition". But if we wait for it