Don't call --random on pumba; note about time

.github/workflows/network/run_pumba.sh

@@ -7,7 +7,9 @@ percent=$2
 rest_node_names=$3
 
 # Build Pumba netem command
-nix_command="nix run github:noonio/pumba/noon/add-flake -- -l debug --random netem --duration 20m"
+# Note: We leave it for 20 minutes; but really it's effectively unlimited. We don't
+# expect any of our tests to run longer than that.
+nix_command="nix run github:noonio/pumba/noon/add-flake -- -l debug netem --duration 20m"
 
 while IFS= read -r network; do
     nix_command+=" --target $network"
@@ -18,4 +20,4 @@ nix_command+=" loss --percent \"$percent\" \"re2:$target_node_name\" &"
 echo "$nix_command"
 
 # Run Pumba netem command
-eval "$nix_command"
+eval "$nix_command"