Move H.264 codec test activation directly behind build flag.

Bug: None
Change-Id: I5dd366aba16b440a8e99826e116db0d6b68bf844
Reviewed-on: https://webrtc-review.googlesource.com/76621
Reviewed-by: Åsa Persson <asapersson@webrtc.org>
Commit-Queue: Rasmus Brandt <brandtr@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23231}

modules/video_coding/codecs/test/videocodec_test_openh264.cc

@@ -19,8 +19,6 @@
 namespace webrtc {
 namespace test {
 
-#if defined(WEBRTC_USE_H264)
-
 namespace {
 // Codec settings.
 const int kCifWidth = 352;
@@ -87,7 +85,5 @@ TEST(VideoProcessorIntegrationTestOpenH264, SingleNalUnit) {
                    &bs_thresholds, nullptr);
 }
 
-#endif  // defined(WEBRTC_USE_H264)
-
 }  // namespace test
 }  // namespace webrtc