Fix invalidate parameter word error

[tungbq]

Connection with issue(s)

Close #1250

Solution description

Fix invalidate parameter word error: shoudlFocus -> shouldFocus

Screenshots or Videos

To Do

• Read contributing guide
• Check the original issue to confirm it is fully satisfied
• Add solution description to help guide reviewers
• Add unit test to verify new or fixed behaviour
• If apply, add documentation to code properties and package readme

[codecov]

Codecov Report

Merging #1251 (ab3b8f7) into main (93507c0) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1251   +/-   ##
=======================================
  Coverage   85.14%   85.14%           
=======================================
  Files          20       20           
  Lines         707      707           
=======================================
  Hits          602      602           
  Misses        105      105           

Impacted Files	Coverage Δ
lib/src/form_builder_field.dart	81.91% <ø> (ø)

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