patch 8.2.3811: the opfunc error test fails on a slow machine

Problem:    The opfunc error test fails on a slow machine.
Solution:   Use WaitForAssert().
diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
index f4a42ce..9dc0d73 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
@@ -3231,6 +3231,7 @@
   call writefile(lines, 'XTest_opfunc_error')
 
   var buf = RunVimInTerminal('-S XTest_opfunc_error', {rows: 6, wait_for_ruler: 0})
+  WaitForAssert(() => assert_match('Press ENTER', term_getline(buf, 6)))
   VerifyScreenDump(buf, 'Test_opfunc_error', {})
 
   # clean up
diff --git a/src/version.c b/src/version.c
index 6ce7173..581fcd7 100644
--- a/src/version.c
+++ b/src/version.c
@@ -750,6 +750,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3811,
+/**/
     3810,
 /**/
     3809,