patch 8.2.0054: :diffget and :diffput don't have good completion

Problem:    :diffget and :diffput don't have good completion.
Solution:   Add proper completion. (Dominique Pelle, closes #5409)
diff --git a/src/version.c b/src/version.c
index 0eaafd1..a099cd3 100644
--- a/src/version.c
+++ b/src/version.c
@@ -743,6 +743,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    54,
+/**/
     53,
 /**/
     52,