patch 9.0.0111: "nocombine" is missing from synIDattr()

Problem:    "nocombine" is missing from synIDattr().
Solution:   Add "nocombine". (Muni Tanjim, closes #10816)
diff --git a/runtime/doc/builtin.txt b/runtime/doc/builtin.txt
index f700d4e..a65f60d 100644
--- a/runtime/doc/builtin.txt
+++ b/runtime/doc/builtin.txt
@@ -9233,6 +9233,7 @@
 		"underline"	"1" if underlined
 		"undercurl"	"1" if undercurled
 		"strike"	"1" if strikethrough
+		"nocombine"	"1" if nocombine
 
 		Returns an empty string on error.