Fix typo in upload_to_s3_spec.rb

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Generated with the help of Claude Code, https://claude.com/claude-code

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: mokagio

spec/upload_to_s3_spec.rb

@@ -273,7 +273,7 @@ def stub_s3_response_for_file(key, exists: true)
           end
         end
 
-        # Untill we remove the deprecated skip_if_exists option, if_exists needs to be optional.
+        # Until we remove the deprecated skip_if_exists option, if_exists needs to be optional.
         # if_exists also has a verify_block that will throw if the given value doesn't match the allowed ones.
         # This test makes sure that if the user omits or set if_exists as nil, Fastlane bypasses the verify_block.
         # This is models a possible usage for the action—we want to be extra careful.