chore: update CoreConcepts.md (#814)

Mention of property "ConnectionString" removed, as this property is no longer part of the ITenantInfo entity.

docs/CoreConcepts.md

@@ -7,7 +7,7 @@ However, there are a few important specifics to be aware of. The items below mak
 
 A `TenantInfo` instance contains information about a tenant. Often this will be the "current" tenant in the context an
 app. These instances' type implements `ITenantInfo` which defines properties
-for `Id`, `Identifier`, `Name`, `ConnectionString`. When calling `AddMultiTenant<TTenantInfo>` the type passed into the
+for `Id`, `Identifier`, `Name`. When calling `AddMultiTenant<TTenantInfo>` the type passed into the
 type parameter defines the`ITenantInfo` use throughout the library and app.
 
 * `Id` is a unique id for a tenant in the app and should never change.