STATE_FDB_TABLE_NAME's key delimiter was conflict between swss-schema.md & orch.h

[Xiangpeng-Sun]

In orch.h, the delimiter of key for tables in state db is defined as state_db_key_delimiter which is '|'. However, in fdborch.cpp ':' is used as delimiter of key for STATE_FDB_TABLE_NAME due to the swss-scheme definition. This conflict does not affect anything so far, but is may confuse further developers which is the right way to code, or it means swss-scheme has a higher priority to follow?