Remove redundant arbitrary config class
Remove redundant arbitrary config class

We had 2 class definitions for CitusCacheManyConnectionsConfig, where
one of them was a copy of CitusSmallCopyBuffersConfig.

This commit leaves the intended class definition that configures caching
many connections, and removes the one that is a copy of another class

citusdata/citus,citusdata/citus,citusdata/citus,citusdata/citus,citusdata/citus