patch 8.2.3648: "verbose pwd" is incorrect after dropping files on Vim

Problem:    "verbose pwd" is incorrect after dropping files on Vim.
Solution:   Set the chdir reason to "drop".
diff --git a/src/version.c b/src/version.c
index 1871c7f..bd41147 100644
--- a/src/version.c
+++ b/src/version.c
@@ -758,6 +758,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3648,
+/**/
     3647,
 /**/
     3646,