update nimble (#22814)

Issues like nim-lang/nimble#1149 keep popping
up. One way or another, we should alleviate the pain.

Finally, we should consider
nim-lang/nimble#1141 (comment) as
an option using some kind of cron script to update
https://nim-lang.org/nimble/packages.json. It's turning into a really
annoying problem.

Author: ringabout

koch.nim

@@ -11,7 +11,7 @@
 
 const
   # examples of possible values for repos: Head, ea82b54
-  NimbleStableCommit = "168416290e49023894fc26106799d6f1fc964a2d" # master
+  NimbleStableCommit = "603e329442059947d63e4c1b2ef5294f1f544485" # master
   AtlasStableCommit = "7b780811a168f3f32bff4822369dda46a7f87f9a"
   ChecksumsStableCommit = "025bcca3915a1b9f19878cea12ad68f9884648fc"