conc024 is flaky on Windows
--- concurrent/should_run/conc024.run/conc024.stdout.normalised 2020-01-23 13:47:47.215534700 +0000
+++ "concurrent\\should_run\\conc024.run\\conc024.run.stdout.normalised" 2020-01-23 13:47:47.215534700 +0000
@@ -1 +0,0 @@
-thread blocked indefinitely in an MVar operation