Sync Gateway : Remove obsolete configuration options

With Sync Gateway 1.5, the following config properties are no longer applicable

• https://docs.couchbase.com/sync-gateway/2.6/config-properties.html#maxCouchbaseConnections
• https://docs.couchbase.com/sync-gateway/2.6/config-properties.html#maxCouchbaseOverflow

Please remove all references to these properties (starting v1.5)

IB Updates:

28Jan - This is applied to 2.6 and 2.7. Needs putting in 1.5-2.5.

• 1.5 https://github.com/couchbase/docs-sync-gateway/pull/165
• 2.0 https://github.com/couchbase/docs-sync-gateway/pull/166
• 2.1 https://github.com/couchbase/docs-sync-gateway/pull/167
• 2.5 https://github.com/couchbase/docs-sync-gateway/pull/168