patch 9.1.0629: Rename of pum hl_group is incomplete

Problem:  Rename of pum hl_group is incomplete in source.
Solution: Also rename the test function.  Rename to user_hlattr in code
          to avoid confusion with pum_extra.  Add test with matched text
          highlighting (zeertzjq).

closes: #15348

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/insert.txt b/runtime/doc/insert.txt
index e85f341..e80fea8 100644
--- a/runtime/doc/insert.txt
+++ b/runtime/doc/insert.txt
@@ -1,4 +1,4 @@
-*insert.txt*    For Vim version 9.1.  Last change: 2024 Jul 25
+*insert.txt*    For Vim version 9.1.  Last change: 2024 Jul 27
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -1183,12 +1183,12 @@
 	user_data	custom data which is associated with the item and
 			available in |v:completed_item|; it can be any type;
 			defaults to an empty string
-	hl_group	allows specifying an additional highlight group to
-			apply extra attributes to completion items in the
-			popupmenu. Is combined with |hl-PmenuSel| and
-			|hl-Pmenu| highlighting attributes to apply cterm and
-			gui properties, such as strikethrough to the
-			completion items.
+	hl_group	an additional highlight group whose attributes are
+			combined with |hl-PmenuSel| and |hl-Pmenu| or
+			|hl-PmenuMatchSel| and |hl-PmenuMatch| highlight
+			attributes in the popup menu to apply cterm and gui
+			properties (with higher priority) like strikethrough
+			to the completion items
 
 All of these except "icase", "equal", "dup" and "empty" must be a string.  If
 an item does not meet these requirements then an error message is given and