Remove old tests that have been migrated to the v8 repo.

LayoutTests/fast/js/script-tests/date-toisostring.js

-description("Tests for Date.toISOString");
-
-function throwsRangeError(str)
-{
-    try {
-        eval(str);
-    } catch (e) {
-        return e instanceof RangeError;
-    }
-    return false;
-}
-
-shouldThrow("Date.toISOString.call({})");
-shouldThrow("Date.toISOString.call(0)");
-
-shouldBe("new Date(-400).toISOString()", "'1969-12-31T23:59:59.600Z'");
-shouldBe("new Date(0).toISOString()", "'1970-01-01T00:00:00.000Z'");
-shouldBe("new Date('1 January 1500 UTC').toISOString()", "'1500-01-01T00:00:00.000Z'");
-shouldBe("new Date('1 January 2000 UTC').toISOString()", "'2000-01-01T00:00:00.000Z'");
-shouldBe("new Date('1 January 4000 UTC').toISOString()", "'4000-01-01T00:00:00.000Z'");
-shouldBe("new Date('1 January 100000 UTC').toISOString()", "'+100000-01-01T00:00:00.000Z'");
-shouldBe("new Date('1 January -1 UTC').toISOString()", "'-000001-01-01T00:00:00.000Z'");
-shouldBe("new Date('10 March 2000 UTC').toISOString()", "'2000-03-10T00:00:00.000Z'");
-shouldBeTrue('throwsRangeError("new Date(NaN).toISOString()")');