patch 8.2.2673: Vim9: script-local funcref can have lower case name

Problem:    Vim9: script-local funcref can have lower case name.
Solution:   Require an upper case name.
diff --git a/src/version.c b/src/version.c
index 602fdb6..fe27425 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2673,
+/**/
     2672,
 /**/
     2671,