patch 8.2.4973: Vim9: type error for list unpack mentions argument

Problem:    Vim9: type error for list unpack mentions argument.
Solution:   Mention variable. (close #10435)
diff --git a/src/testdir/test_vim9_disassemble.vim b/src/testdir/test_vim9_disassemble.vim
index 3ab3c0d..c99c8b4 100644
--- a/src/testdir/test_vim9_disassemble.vim
+++ b/src/testdir/test_vim9_disassemble.vim
@@ -581,10 +581,10 @@
         '\d CHECKTYPE list<any> stack\[-1\]\_s*' ..
         '\d CHECKLEN >= 2\_s*' ..
         '\d\+ ITEM 0\_s*' ..
-        '\d\+ CHECKTYPE string stack\[-1\] arg 1\_s*' ..
+        '\d\+ CHECKTYPE string stack\[-1\] var 1\_s*' ..
         '\d\+ STORE $0\_s*' ..
         '\d\+ ITEM 1\_s*' ..
-        '\d\+ CHECKTYPE string stack\[-1\] arg 2\_s*' ..
+        '\d\+ CHECKTYPE string stack\[-1\] var 2\_s*' ..
         '\d\+ STORE $1\_s*' ..
         '\d\+ SLICE 2\_s*' ..
         '\d\+ STORE $2\_s*' ..