Fix all `s/trough/through/`

```
% git grep -n trough
activerecord/test/cases/associations/has_many_through_associations_test.rb:1253:  def test_has_many_trough_with_scope_that_has_joined_same_table_with_parent_relation
```

activerecord/test/cases/associations/has_many_through_associations_test.rb

@@ -1250,7 +1250,7 @@ def test_has_many_through_do_not_cache_association_reader_if_the_though_method_h
     TenantMembership.current_member = nil
   end
 
-  def test_has_many_trough_with_scope_that_has_joined_same_table_with_parent_relation
+  def test_has_many_through_with_scope_that_has_joined_same_table_with_parent_relation
     assert_equal authors(:david), Author.joins(:comments_for_first_author).take
   end