[gnome-sdk-images] Bump vala source tarball to 0.40.7

[Rico Tzschichholz <ricotz src gnome org>]

commit 8695ed3c689979467a1f2c36669c5f09dad60f65
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Thu Jun 21 16:13:10 2018 +0200

    Bump vala source tarball to 0.40.7

 org.gnome.Sdk.json.in | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/org.gnome.Sdk.json.in b/org.gnome.Sdk.json.in
index 53ea7ef..f9fd10c 100644
--- a/org.gnome.Sdk.json.in
+++ b/org.gnome.Sdk.json.in
@@ -190,8 +190,8 @@
             "sources": [
                 {
                     "type": "archive",
-                    "url": "https://download.gnome.org/sources/vala/0.40/vala-0.40.6.tar.xz";,
-                    "sha256": "6da450f1a73e0f1e17506e68cce5b9e8996349e576d3f8cb6b0b73ee22e44be2"
+                    "url": "https://download.gnome.org/sources/vala/0.40/vala-0.40.7.tar.xz";,
+                    "sha256": "bee662f60ab3a0d5266c1dd66f508cd9ed3254d74622d23c2d6bd94c91990aec"
                 },
                 {
                     "type": "patch",