More mtimedelay tweaking

WSL was still flaky

Author: timholy

test/common.jl

@@ -20,7 +20,7 @@ end
 @static if Sys.isapple()
     const mtimedelay = 3.1  # so the defining files are old enough not to trigger mtime criterion
 elseif Sys.islinux() && isfile("/etc/wsl.conf")   # WSL
-    const mtimedelay = 2.0
+    const mtimedelay = 3.0
 else
     const mtimedelay = 0.1
 end