[pitivi] Don't require gst-validate to be available

[Thibault Saunier <tsaunier src gnome org>]

commit 40dbcc14dc3d5b91b22a1d7e168aad5b5bfe55c3
Author: Sebastian Dröge <sebastian centricular com>
Date:   Sun Sep 24 09:45:55 2017 +0300

    Don't require gst-validate to be available
    
    Fixes T7838

 tests/meson.build |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/tests/meson.build b/tests/meson.build
index 481ce14..bfde4e6 100644
--- a/tests/meson.build
+++ b/tests/meson.build
@@ -1,4 +1,4 @@
-runtests = find_program('gst-validate-launcher', required : true)
+runtests = find_program('gst-validate-launcher', required : false)
 
 if runtests.found()
     test('Pitivi unit tests', runtests,