patch 8.1.1638: running tests leaves some files behind

Problem:    Running tests leaves some files behind.
Solution:   Delete the files. (Ozaki Kiichi, closes #4617)
diff --git a/src/version.c b/src/version.c
index b5aac1a..c835eee 100644
--- a/src/version.c
+++ b/src/version.c
@@ -778,6 +778,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1638,
+/**/
     1637,
 /**/
     1636,