Fix documented fallback of database option (#159)

It was `PGUSER` first at one point, and now falls back to the actual `user` value used.

Co-authored-by: Charmander <[email protected]>

Author: haraldschilly

content/api/2-client.mdx

@@ -14,7 +14,7 @@ config = {
   user?: string, // default process.env.PGUSER || process.env.USER
   password?: string or function, //default process.env.PGPASSWORD
   host?: string, // default process.env.PGHOST
-  database?: string, // default process.env.PGDATABASE || process.env.USER
+  database?: string, // default process.env.PGDATABASE || user
   port?: number, // default process.env.PGPORT
   connectionString?: string, // e.g. postgres://user:password@host:5432/database
   ssl?: any, // passed directly to node.TLSSocket, supports all tls.connect options