Update version to 18.2.1

Signed-off-by: Juan A. Suarez Romero <jasuarez@igalia.com>
diff --git a/VERSION b/VERSION
index 08e3ca9..c0aa6d4 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-18.2.0
+18.2.1