Feature: Remove deprecated default exports from @lexical/react modules

[etrepum]

Follow-up to #6088

Now that the default exports from the @lexical/react modules are deprecated in the v0.16.0 release we should plan to remove them. Possibly in the next minor version or after some amount of time has elapsed? I don't know what the typical deprecation schedule looks like in lexical at this <1.0 stage.

This is isolated to the @lexical/rect package and affects the following modules:

• @lexical/react/LexicalClickableLinkPlugin (now exports name ClickableLinkPlugin)
• @lexical/react/LexicalErrorBoundary (now exports name LexicalErrorBoundary)
• @lexical/react/LexicalTableOfContents -> @lexical/react/LexicalTableOfContentsPlugin(which exports name TableOfContentsPlugin) - the old module still exists with only a default export
• @lexical/react/useLexicalEditable (now exports name useLexicalEditable)
• @lexical/react/useLexicalSubscription (now exports name useLexicalSubscription)