Fixes by misspell-fixer (#674)

Co-authored-by: sobolevn <sobolevn@users.noreply.github.com>

tests/typecheck/managers/querysets/test_annotate.yml

@@ -244,7 +244,7 @@
                     username = models.CharField(max_length=100)
 
 
--   case: annotate_currently_allows_lookups_of_non_existant_field
+-   case: annotate_currently_allows_lookups_of_non_existent_field
     main: |
         from myapp.models import User
         from django.db.models.expressions import F