Update varnish package cloud repo files.

pkg/rpm/varnishcache_varnish5.repo

-[varnishcache_varnish5]
-name=varnishcache_varnish5
-baseurl=https://packagecloud.io/varnishcache/varnish5/el/7/$basearch
-repo_gpgcheck=1
-gpgcheck=0
-enabled=1
-gpgkey=https://packagecloud.io/varnishcache/varnish5/gpgkey
-sslverify=1
-sslcacert=/etc/pki/tls/certs/ca-bundle.crt
-metadata_expire=300
-
-[varnishcache_varnish5-source]
-name=varnishcache_varnish5-source
-baseurl=https://packagecloud.io/varnishcache/varnish5/el/7/SRPMS
-repo_gpgcheck=1
-gpgcheck=0
-enabled=1
-gpgkey=https://packagecloud.io/varnishcache/varnish5/gpgkey
-sslverify=1
-sslcacert=/etc/pki/tls/certs/ca-bundle.crt
-metadata_expire=300
-

pkg/rpm/varnishcache_varnish61.repo → pkg/rpm/varnishcache_varnish66.repo

-[varnishcache_varnish61]
-name=varnishcache_varnish61
-baseurl=https://packagecloud.io/varnishcache/varnish61/el/7/$basearch
+[varnishcache_varnish66]
+name=varnishcache_varnish66
+baseurl=https://packagecloud.io/varnishcache/varnish66/el/7/$basearch
 repo_gpgcheck=1
 gpgcheck=0
 enabled=1
-gpgkey=https://packagecloud.io/varnishcache/varnish61/gpgkey
+gpgkey=https://packagecloud.io/varnishcache/varnish66/gpgkey
 sslverify=1
 sslcacert=/etc/pki/tls/certs/ca-bundle.crt
 metadata_expire=300
 
-[varnishcache_varnish61-source]
-name=varnishcache_varnish61-source
-baseurl=https://packagecloud.io/varnishcache/varnish61/el/7/SRPMS
+[varnishcache_varnish66-source]
+name=varnishcache_varnish66-source
+baseurl=https://packagecloud.io/varnishcache/varnish66/el/7/SRPMS
 repo_gpgcheck=1
 gpgcheck=0
 enabled=1
-gpgkey=https://packagecloud.io/varnishcache/varnish61/gpgkey
+gpgkey=https://packagecloud.io/varnishcache/varnish66/gpgkey
 sslverify=1
 sslcacert=/etc/pki/tls/certs/ca-bundle.crt
 metadata_expire=300