poky.conf: Bump version for 2.7.4 warrior release

(From meta-yocto rev: e16269fae87b674a686c96488daa2120f0ea8ba7)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta-poky/conf/distro/poky.conf

@@ -1,6 +1,6 @@
 DISTRO = "poky"
 DISTRO_NAME = "Poky (Yocto Project Reference Distro)"
-DISTRO_VERSION = "2.7.3"
+DISTRO_VERSION = "2.7.4"
 DISTRO_CODENAME = "warrior"
 SDK_VENDOR = "-pokysdk"
 SDK_VERSION = "${@d.getVar('DISTRO_VERSION').replace('snapshot-${DATE}', 'snapshot')}"