manifests: remove prometheus.io/scrape annotations

These annotations made sense in pre v1.3.0 Prometheus releases, however,
with >=v1.3.0 and the Prometheus Operator these annotations are more
confusing then helpful.

manifests/etcd/etcd-bootkube-vagrant-multi.yaml

@@ -5,8 +5,6 @@ metadata:
   labels:
     app: etcd
     etcd: k8s
-  annotations:
-    prometheus.io/scrape: 'true'
 spec:
   type: ClusterIP
   clusterIP: None
@@ -29,4 +27,4 @@ subsets:
   ports:
   - name: api
     port: 2379
-    protocol: TCP
+    protocol: TCP