patch 8.2.4892: test failures because of changed error messages

Problem:    Test failures because of changed error messages.
Solution:   Adjust the exptected error messages.
diff --git a/src/testdir/test_vim9_expr.vim b/src/testdir/test_vim9_expr.vim
index 729e77a..40d759c 100644
--- a/src/testdir/test_vim9_expr.vim
+++ b/src/testdir/test_vim9_expr.vim
@@ -3114,7 +3114,7 @@
   v9.CheckDefExecAndScriptFailure(['echo g:testblob[2]'], 'E979:', 1)
   v9.CheckDefExecAndScriptFailure(['echo g:testblob[-3]'], 'E979:', 1)
 
-  v9.CheckDefExecAndScriptFailure(['echo g:testlist[4]'], 'E684: list index out of range: 4', 1)
+  v9.CheckDefExecAndScriptFailure(['echo g:testlist[4]'], 'E684: List index out of range: 4', 1)
   v9.CheckDefExecAndScriptFailure(['echo g:testlist[-5]'], 'E684:', 1)
 
   v9.CheckDefExecAndScriptFailure(['echo g:testdict["a" : "b"]'], 'E719:', 1)