patch 8.2.0833: mapping <C-bslash> doesn't work in the GUI

Problem:    Mapping <C-bslash> doesn't work in the GUI.
Solution:   Reset seenModifyOtherKeys when starting the GUI. (closes #6150)
diff --git a/src/version.c b/src/version.c
index 463025c..44f7f26 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    833,
+/**/
     832,
 /**/
     831,