Fix testsuite

[andreasabel]

stm/tests[master]$ ./runtests.sh 
using GHC version: 9.10.1
== running test 'T15136'
Loaded package environment from /Users/abel/bin/src/stm/.ghc.environment.x86_64-darwin-9.10.1
[1 of 2] Compiling Main             ( T15136.hs, T15136.o )
[2 of 2] Linking T15136
validate stdout output...
--- T15136.stdout	2024-04-13 10:30:37.000000000 +0200
+++ T15136.stdout.run	2024-08-01 07:44:55.000000000 +0200
@@ -1 +0,0 @@
-1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 
\ No newline at end of file