msh testsuite: fix false positive, tweak run stript

diff --git a/shell/msh_test/msh-execution/exitcode_EACCES.right b/shell/msh_test/msh-execution/exitcode_EACCES.right
index b13682c..6e5480b 100644
--- a/shell/msh_test/msh-execution/exitcode_EACCES.right
+++ b/shell/msh_test/msh-execution/exitcode_EACCES.right
@@ -1,2 +1,2 @@
-./: cannot execute
+./: can't execute
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