Make inherited scope test fail

This triggers the JoinDependency work to reflect on the associations
and trigger an error as follows:

  ActiveRecord::ConfigurationError: Association named 'account' was
  not found on Company; perhaps you misspelled it?

Fix Company.of_first_firm joins association name

Should be `Company.joins(:accounts)` not `Company.joins(:account)`.

Do the same for Client.of_first_firm

activerecord/test/cases/inheritance_test.rb

@@ -352,8 +352,8 @@ def test_inheritance_without_mapping
   end
 
   def test_scope_inherited_properly
-    assert_nothing_raised { Company.of_first_firm }
-    assert_nothing_raised { Client.of_first_firm }
+    assert_nothing_raised { Company.of_first_firm.to_sql }
+    assert_nothing_raised { Client.of_first_firm.to_sql }
   end
 end
 

activerecord/test/models/company.rb

@@ -12,7 +12,7 @@ class Company < AbstractCompany
   has_many :developers, :through => :contracts
 
   scope :of_first_firm, lambda {
-    joins(:account => :firm).
+    joins(:accounts => :firm).
     where('firms.id' => 1)
   }