package/patch: fix CVE-2018-20969

do_ed_script in pch.c in GNU patch through 2.7.6 does not block strings
beginning with a ! character. NOTE: this is the same commit as for
CVE-2019-13638, but the ! syntax is specific to ed, and is unrelated to
a shell metacharacter.

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>