Connectors - remove SQL queries to discern relationships

[MikeStall]

SQL allows joins on any fields and does not tell us the join relationships.

This code was intended to get the relationships from SQL (similar to how we can get relationships from Dataverse):

Power-Fx/src/libraries/Microsoft.PowerFx.Connectors/Tabular/CdpTableResolver.cs

Line 75 in 07a817b

@"{""query"":""SELECT fk.name AS FK_Name, '[' + sp.name + '].[' + tp.name + ']' AS Parent_Table, cp.name AS Parent_Column, '[' + sr.name + '].[' + tr.name + ']' AS Referenced_Table, cr.name AS Referenced_Column" +

(This was added relatively recently in #2550)

But it is not correct and should be removed. (Instead, it's telling us foreign key constraints. )

This means expressions would be written like:
LookUp(Table2, ThisRecord.Id2 = Id1).Field2

rather than
_tabld1Record.Id1.Field2

The LookUp is consistent with what PowerApps does today.