[gnome-todo] project: fix wrong markdown

[Gitlab System User <gitlab src gnome org>]

commit bfa34222abeb8ae954c62d0bf6d5efc2456ee799
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Mon Oct 16 22:53:37 2017 -0200

    project: fix wrong markdown

 CONTRIBUTING.md | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 646f4f0..93dc975 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -60,7 +60,7 @@ This is how it would look with a maximum width of 650px:
 1. Ensure your code compiles. Run `make` before creating the pull request.
 2. If you're adding new external API, it must be properly documented.
 3. The commit message is formatted as follows:
-   ```
+```
    component: <summary>
 
    A paragraph explaining the problem and its context.
@@ -68,7 +68,7 @@ This is how it would look with a maximum width of 650px:
    Another one explaining how you solved that.
 
    <link to the bug ticket>
-   ```
+```
 4. You may merge the pull request in once you have the sign-off of the maintainers, or if you
    do not have permission to do that, you may request the second reviewer to merge it for you.