package/libmodsecurity: select pcre2

Commit ea746f31 forgot to select pcre2
resulting in the following build failure:

Makefile:575: *** pcre2 is in the dependency chain of libmodsecurity that has added it to its _DEPENDENCIES variable without selecting it or depending on it from Config.in.  Stop.

Fixes:
 - http://autobuild.buildroot.org/results/6528d2611bd1a45c1e94bc6b866de9c33dd90a7b



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