recipes: Drop remaining PR values from recipes

* as oe-core did in:
  https://git.openembedded.org/openembedded-core/commit/?id=d4c346e8ab

* when people are have to maintain own PRs for recipes in oe-core, they
  might add them for meta-oe recipes at the same time when upgrading
  to next LTS

Signed-off-by: Martin Jansa <martin.jansa@gmail.com>
Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-networking/recipes-protocols/zeroconf/zeroconf_0.9.bb

@@ -13,7 +13,6 @@ LIC_FILES_CHKSUM = "file://COPYING;md5=4325afd396febcb659c36b49533135d4 \
                     file://zeroconf.c;beginline=1;endline=13;md5=a5bada96e1e34b08eb7446b28e2630b2"
 SECTION = "net"
 
-PR = "r1"
 
 SRC_URI = "http://www.progsoc.org/~wildfire/zeroconf/download/${BPN}-${PV}.tar.gz \
            file://compilefix.patch \