[gnome-sdk-images] Update vala

[Mathieu Bridon <mbridon src gnome org>]

commit e76ae2c2c1cf635792b7734d3d6d95bd1d12dc44
Author: Mathieu Bridon <bochecha daitauha fr>
Date:   Wed Oct 3 17:01:54 2018 +0200

    Update vala

 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 da3900d..c9469d7 100644
--- a/org.gnome.Sdk.json.in
+++ b/org.gnome.Sdk.json.in
@@ -186,8 +186,8 @@
             "sources": [
                 {
                     "type": "archive",
-                    "url": "https://download.gnome.org/sources/vala/0.40/vala-0.40.7.tar.xz";,
-                    "sha256": "bee662f60ab3a0d5266c1dd66f508cd9ed3254d74622d23c2d6bd94c91990aec"
+                    "url": "https://download.gnome.org/sources/vala/0.42/vala-0.42.2.tar.xz";,
+                    "sha256": "9e89aa42152b1cef551568f827aa2deea2a9b5487d78c91474c8617b618e5f07"
                 },
                 {
                     "type": "patch",