Refactor foreign keys and clean up test setup

Updated foreign key references in PostgreSQL schema tests to match
actual column names, improving alignment with the database schema.
Removed unnecessary delay in SQLite schema tests to speed up
test execution. Corrected file deletion in migration tests to target
the correct test database file.

spec/adapters/postgres_schema_spec.cr

@@ -134,13 +134,13 @@ describe Cql::Schema do
       primary :customer_id, Int64, auto_increment: true
       column :customer_name, String, as: "cust_name"
       column :city, String
-      column :country, Int64
+      column :country_id, Int64
     end
 
     Example.customers.create!
 
     Example.alter :customers do
-      foreign_key :fk_country, [:country], :countries, [:country_id]
+      foreign_key :fk_country, [:country_id], :countries, [:id]
     end
   end
 
@@ -158,7 +158,7 @@ describe Cql::Schema do
     Example.customers.create!
 
     Example.alter :customers do
-      foreign_key :fk_country, [:country_id], :countries, [:country_id]
+      foreign_key :fk_country, [:country_id], :countries, [:id]
     end
 
     Example.alter :customers do

spec/adapters/sqlite_schema_spec.cr

@@ -23,10 +23,6 @@ describe Cql::Schema do
     end
   end
 
-  before_each do
-    sleep 1.seconds
-  end
-
   it "creates a table" do
     Data.customers.drop!
     Data.customers.create!

spec/migration_spec.cr

@@ -5,7 +5,7 @@ describe Cql::Migration do
   migrator = Northwind.migrator
 
   after_all do
-    File.delete("spec/db/data.db")
+    File.delete("spec/db/northwind.db")
   end
 
   it "has a migration" do