patch 8.1.0750: when the last sign is deleted the signcolumn may remain

Problem:    When the last sign is deleted the signcolumn may not be removed
            even though 'signcolumn' is "auto".
Solution:   When deleting the last sign redraw the buffer. (Dominique Pelle,
            closes #3803, closes #3804)
diff --git a/src/version.c b/src/version.c
index c0a91d3..b0f4886 100644
--- a/src/version.c
+++ b/src/version.c
@@ -796,6 +796,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    750,
+/**/
     749,
 /**/
     748,