test: update expected value for cairo 1.15

GitHub: fix #50

Reported by Mamoru TASAKA. Thanks!!!

Author: kou

test/test_recording_surface.rb

@@ -15,6 +15,10 @@ def test_new
       context.line_to(80, 100)
       context.stroke
     end
-    assert_equal([10.0, 20.0, 61.0, 61.0], surface.ink_extents)
+    if Cairo.satisfied_version?(1, 15)
+      assert_equal([14.0, 29.0, 67.0, 72.0], surface.ink_extents)
+    else
+      assert_equal([10.0, 20.0, 61.0, 61.0], surface.ink_extents)
+    end
   end
 end