fix: incorrect cursor position after new line

[LucasXu0]

q.mp4

[codecov]

Codecov Report

Attention: Patch coverage is 64.00000% with 9 lines in your changes missing coverage. Please review.

Project coverage is 74.81%. Comparing base (067c8e7) to head (8accda7).
Report is 1 commits behind head on main.

Files	Patch %	Lines
.../block_component/rich_text/appflowy_rich_text.dart	64.00%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #817      +/-   ##
==========================================
- Coverage   74.88%   74.81%   -0.08%     
==========================================
  Files         301      301              
  Lines       14201    14196       -5     
==========================================
- Hits        10635    10621      -14     
- Misses       3566     3575       +9     

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