patch 8.2.1984: cannot use :vimgrep in omni completion

Problem:    Cannot use :vimgrep in omni completion, causing C completion to
            fail.
Solution:   Add the EX_LOCK_OK flag to :vimgrep. (closes #7292)
diff --git a/src/version.c b/src/version.c
index 43cd9cb..8d21a4a 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1984,
+/**/
     1983,
 /**/
     1982,