patch 9.0.1483: += operator does not work on class member

Problem:    += operator does not work on class member.
Solution:   Do not skip as if "this." was used. (Christian Brabandt,
            closes #12263)
diff --git a/src/version.c b/src/version.c
index aa480c1..842b583 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1483,
+/**/
     1482,
 /**/
     1481,