Lexical version: 0.44

Steps To Reproduce

1. Insert Collapsible Container
2. Press Shift + Enter within the container's content

Link to code example: https://playground.lexical.dev/#doc=H4sIAAAAAAAAE9VTzU7DMAx-FeRzmDpWMZYH4Dyp3BCHrDFbJC-uXHdQTX13lG5oXZGQUDnAKbEtfz92cgT0QVkKdYpgjyDMms5yF8gLRrDPo8CjukBgMwOvLHun_XXPHsFCTBkCA7W2lBJgQPFdwcLaiduKq3Yp1Vap2FcMHFDqwBHsvHsx4INgqX0cG6ILS8IK0WM8MZ4xqgHsBejE-njRl8LiU1NnvjP4K26fghL-Aac_pymZyFV12BDe6tnFQPf16KbBlxw1lScOZgzpQkQZDYmrpFelwS_Ln_ygbzZI_PYvl91_9yupnQFytRbugB7sfLlcLe6y1eL-IcsN1NxImfrW5NqtcBP9sBuyWZ7PMug-ABxYbVFXBAAA

The current behavior

• Pressing Shift + Enter does not insert a line break and causes an error to be logged in the console
• If you press Enter, a new paragraph is created at the end of the document

The expected behavior

• Pressing Shift + Enter correctly inserts a line break
• Pressing Enter creates a paragraph inside CollapsibleContent

Impact of fix