renamed nhs to national_health_service (#2923)

* renamed nhs to national_health_service

* Reverted Gemfile.lock

Author: keshavbiswa

lib/faker/default/nhs.rb renamed to lib/faker/default/national_health_service.rb

@@ -11,17 +11,17 @@ def test_nhs_british_number
     assert_match(/\A\d{3}\s\d{3}\s\d{4}\z/, @tester.british_number)
   end
 
-  def test_nhs_check_digit_equals_10
+  def test_check_digit_equals_10
     Faker::NationalHealthService.stub(:rand, 458_617_434) do
       assert_match('458 617 4331', @tester.british_number)
     end
   end
 
-  def test_nhs_check_digit
+  def test_check_digit
     assert_equal 6, @tester.check_digit(number: 400_012_114)
   end
 
-  def test_nhs_check_digit_11
+  def test_check_digit_11
     assert_equal 0, @tester.check_digit(number: 418_513_625)
   end
 end