[folks] Properly rename CONTRIBUTING.md

[Niels De Graef <nielsdg src gnome org>]

commit baa456be4eba1dcbc3c24551f48dc3170f4924c1
Author: Niels De Graef <nielsdegraef gmail com>
Date:   Sun Jun 7 14:28:14 2020 +0200

    Properly rename CONTRIBUTING.md

 CONTRIBUTIONS.md => CONTRIBUTING.md | 0
 README.md                           | 2 +-
 2 files changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/CONTRIBUTIONS.md b/CONTRIBUTING.md
similarity index 100%
rename from CONTRIBUTIONS.md
rename to CONTRIBUTING.md
diff --git a/README.md b/README.md
index 6400e7c1..5b0bdd6f 100644
--- a/README.md
+++ b/README.md
@@ -25,7 +25,7 @@ Please try to add reproducible steps and the relevant version of libfolks.
 If you want to contribute functionality or bug fixes, please open a Merge
 Request (MR). For more info on how to do this, see GitLab's [help pages on
 MR's]. Please also follow our coding conventions, as described in
-CONTRIBUTIONS.md
+CONTRIBUTING.md
 
 If libfolks is not translated in your language or you believe that the current
 translation has errors, you can join one of the various translation teams in