[gnome-continuous] Use an earlier commit for the gst-plugins-base tag

[Emmanuele Bassi <ebassi src gnome org>]

commit 274afb55aa43072d8acb38e6342f31d9ec579db0
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Fri Jun 29 10:50:56 2018 +0100

    Use an earlier commit for the gst-plugins-base tag

 manifest.json | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/manifest.json b/manifest.json
index 070964e..254be89 100644
--- a/manifest.json
+++ b/manifest.json
@@ -702,7 +702,7 @@
                  "config-opts": ["-Denable-gtk-doc=false"]},
 
                {"src": "fd-gstreamer:gst-plugins-base",
-                 "tag": "9f516077233dcd0986e94c769cd605b01ecba41b",
+                 "tag": "1c8bf44dea2af3b8bbed3e230479fe5405a5bad6",
                  "tag-reason": "Build failure using Meson",
                 "config-opts": ["-Ddisable_gtkdoc=true"]},