patch 8.2.4416: Vim9: using a script-local function requires using "s:"

Problem:    Vim9: using a script-local function requires using "s:" when
            setting 'completefunc'.
Solution:   Do not require "s:" in Vim9 script. (closes #9796)
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index 1d3f768..8fcbc99 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -383,12 +383,22 @@
 	set opfunc=function('MyOpFunc')
 	set opfunc=funcref('MyOpFunc')
 	set opfunc={a\ ->\ MyOpFunc(a)}
-	" set using a funcref variable
+
+Set to a script-local function: >
+	set opfunc=s:MyLocalFunc
+	set opfunc=<SID>MyLocalFunc
+In |Vim9| script the "s:" and "<SID>" can be omitted if the function exists in
+the script: >
+	set opfunc=MyLocalFunc
+
+Set using a funcref variable: >
 	let Fn = function('MyTagFunc')
 	let &tagfunc = Fn
-	" set using a lambda expression
+
+Set using a lambda expression: >
 	let &tagfunc = {t -> MyTagFunc(t)}
-	" set using a variable with lambda expression
+
+Set using a variable with lambda expression: >
 	let L = {a, b, c -> MyTagFunc(a, b , c)}
 	let &tagfunc = L