integration: remove check if on us-central-1

There's no obvious reason why those tests can only be run on
us-central-1, remove the check.

It was added with 1577b90c6

integration/300_internet_edge_test.sh

@@ -5,12 +5,6 @@
 
 start_suite "Test short lived connections from the Internet"
 
-if ! echo "$HOST1" | grep "us-central1-a"; then
-    echo "Skipping; test needs to be run against VMs on GCE."
-    scope_end_suite
-    exit
-fi
-
 weave_on "$HOST1" launch
 scope_on "$HOST1" launch
 docker_on "$HOST1" run -d -p 80:80 --name nginx nginx