some of the updated extensions will recreate the supporting files in a new location in the webassist folder.
the error is saying that there is a require once line to include the supporting file from this location:
WA_ValidationToolkit\WAVT_ValidatedForm_PHP.php
and another one to include the supporting file from this location:
webassist\form_validations\wavt_validated form_php.php
you should delete the the require once line that references the old file at:
WA_ValidationToolkit\WAVT_ValidatedForm_PHP.php