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

[jameshfisher]

Description
This reverts #4868.

The issue reported at #4862 is a valid complaint, but the change is not an appropriate fix. It is a serious breaking change, reported in #5153.

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.

Issue
Fixes: #5153

Checks

• The new code matches the existing patterns and styles.
• The tests pass with yarn test.
• The linter passes with yarn lint. (Fix errors with yarn fix.)
• The relevant examples still work. (Run examples with yarn start.)
• You've added a changeset if changing functionality. (Add one with yarn changeset add.)

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Latest commit: 658cd82

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[jameshfisher]

Thanks @dylans !