run-tests: remove use of FILE_BINARY constant

run-tests: remove use of FILE_BINARY constant

The FILE_BINARY (and FILE_TEXT) constants are not really valid or useful
constants. It looks like they were added in 5.2.7 and have "no effect,
and are only available for forward compatibility."

See: https://www.php.net/manual/en/filesystem.constants.php

The default value of the file_put_contents() flags parameter is 0 and
FILE_BINARY is set to 0, so removing it doesn't change functionality.

P.S. Maybe those constants should be deprecated or removed in 8.0.

Closes GH-5556.