t4034: diff.*.wordregex should not be "sticky" in --word-diff

The test case applies a custom wordRegex to one file in a diff, and expects
that the default word splitting applies to the second file in the diff.
But the custom wordRegex is also incorrectly used for the second file.

Helped-by: Thomas Rast <trast@student.ethz.ch>
Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>