validate-scenario: reflow #ifdef to work around bogus g-ir-scanner warning

Looks like a scanner bug.

The endif comments are the wrong way round too, but that's not it.

gst-validate-scenario.c:126: mismatched #endif  /* G_HAVE_GNUC_VARARGS */

Part-of: <gstreamer/gst-devtools!213>
37 jobs for !213 with gir-warning in 51 minutes and 46 seconds (queued for 7 seconds)
detached
Status Job ID Name Coverage
  Build Docker
passed #3800493
alpine amd64 manifest builder docker

00:00:20

passed #3800492
android docker

00:00:16

passed #3800490
cerbero fedora amd64 docker

00:00:19

passed #3800489
fedora amd64 docker

00:02:51

passed #3800495
gst-indent amd64 docker

00:00:20

 
  Preparation
passed #3800499
gst indent

00:00:19

passed #3800497
manifest

00:00:55

 
  Build
passed #3800517
gstreamer
build cerbero cross-android universal

00:11:38

passed #3800525
gst-ios-13.2
build cerbero cross-ios universal

00:19:55

passed #3800519
gstreamer
build cerbero cross win32

00:08:39

passed #3800521
gstreamer
build cerbero cross win64

00:05:30

passed #3800515
gstreamer
build cerbero fedora x86_64

00:05:47

passed #3800523
gst-macos-10.15
build cerbero macos x86_64

00:10:21

passed #3800506
build clang fedora x86_64

00:04:48

manual #3800512
1809 windows docker allowed to fail manual
build msys2
passed #3800501
build nodebug fedora x86_64

00:04:24

passed #3800502
build static fedora x86_64

00:04:29

passed #3800504
build static nodebug fedora x86_64

00:04:29

passed #3800507
1809 windows docker
build vs2017 amd64

00:12:39

passed #3800510
1809 windows docker
build vs2017 x86

00:12:19

 
  Test
passed #3800527
gstreamer
check fedora

00:06:18

passed #3800529
gstreamer
integration testsuites fedora 1/4

00:15:40

passed #3800532
gstreamer
integration testsuites fedora 2/4

00:14:27

passed #3800533
gstreamer
integration testsuites fedora 3/4

00:14:14

passed #3800534
gstreamer
integration testsuites fedora 4/4

00:14:25

passed #3800539
gstreamer
valgrind bad

00:06:23

passed #3800536
gstreamer
valgrind base

00:06:01

passed #3800611
gstreamer
valgrind core

00:21:52

passed #3800804
gstreamer
valgrind ges

00:06:48

passed #3800537
gstreamer
valgrind good

00:09:56

passed #3800538
gstreamer
valgrind ugly

00:04:04

failed #3800535
gstreamer
valgrind core

00:19:40

failed #3800540
gstreamer
valgrind ges

00:16:17

failed #3800612
gstreamer
valgrind ges

00:17:02

 
  Integrate
passed #3800541
cross-android universal examples

00:08:10

passed #3800543
gst-ios-13.2
cross-ios universal examples

00:01:16

passed #3800542
documentation

00:13:06