Typo fix at UploadedFile.php documentation
minor #10460 Typo fix at UploadedFile.php documentation (jbruni)

This PR was submitted for the 2.3-dev branch but it was merged into the 2.3 branch instead (closes #10460).

Discussion
----------

Typo fix at UploadedFile.php documentation

Commits
-------

ced3f04 Typo fix at UploadedFile.php documentation