remove workarounds for Windows native CPU features

bug fixed in LLVM 10

closes #508

lib/std/fmt/parse_float.zig

@@ -382,10 +382,6 @@ pub fn parseFloat(comptime T: type, s: []const u8) !T {
 }
 
 test "fmt.parseFloat" {
-    if (std.Target.current.isWindows()) {
-        // TODO https://github.com/ziglang/zig/issues/508
-        return error.SkipZigTest;
-    }
     const testing = std.testing;
     const expect = testing.expect;
     const expectEqual = testing.expectEqual;