Use 8 test runner shards here

(cherry picked from commit 49239c1)

Author: michaelklishin

deps/rabbit/BUILD.bazel

@@ -309,7 +309,7 @@ rabbitmq_integration_suite(
 rabbitmq_integration_suite(
     name = "classic_queue_prop_SUITE",
     size = "large",
-    shard_count = 6,
+    shard_count = 8,
     sharding_method = "case",
     deps = [
         "@proper//:erlang_app",