patch 8.2.5165: import test fails because 'diffexpr' isn't reset

Problem:    Import test fails because 'diffexpr' isn't reset.
Solution:   Reset 'diffexpr'.
diff --git a/src/version.c b/src/version.c
index d7f0a83..8e396cd 100644
--- a/src/version.c
+++ b/src/version.c
@@ -736,6 +736,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    5165,
+/**/
     5164,
 /**/
     5163,