Improve the mtimedelay change

Author: timholy

test/common.jl

@@ -19,8 +19,10 @@ 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
 else
-    const mtimedelay = 0.2
+    const mtimedelay = 0.1
 end
 
 yry() = (sleep(mtimedelay); revise(); sleep(mtimedelay))