Update the test for negative zero in NumberFormat.

The specification was updated in https://github.com/tc39/ecma402/pull/232.

test/intl402/NumberFormat/prototype/format/format-negative-numbers.js

@@ -6,6 +6,11 @@ es5id: 11.3.2_FN_1
 description: >
     Tests that Intl.NumberFormat.prototype.format  doesn't treat all
     numbers as negative.
+info: |
+    PartitionNumberPattern ( numberFormat, x )
+    1. If x is not NaN and x < 0 or _x_ is -0, then
+       a. Let _x_ be -_x_.
+       b. Let _pattern_ be _numberFormat_.[[NegativePattern]].
 author: Roozbeh Pournader
 ---*/
 
@@ -13,4 +18,4 @@ var formatter = new Intl.NumberFormat();
   
 assert.notSameValue(formatter.format(1), formatter.format(-1), 'Intl.NumberFormat is formatting 1 and -1 the same way.');
 
-assert.sameValue(formatter.format(-0), formatter.format(0), 'Intl.NumberFormat is formatting signed zeros differently.');
+assert.notSameValue(formatter.format(0), formatter.format(-0), 'Intl.NumberFormat is formatting 0 and -0 the same way.');