Fix typo in .pc file
Fix typo in .pc file

Requires.Private should be Requires.private.

https://bugzilla.gnome.org/show_bug.cgi?id=721719

Distrotech/at-spi2-atk,GNOME/at-spi2-core,GNOME/at-spi2-core,GNOME/at-spi2-core,Distrotech/at-spi2-atk,GNOME/at-spi2-atk