nix: increase jwt-hs loadtest TOTAL_TARGETS

This is so the process monitoring results are more meaningful.

* remove the amount of total targets from the loadtest kind name
  since the targets can change.

* clarifies the top comment on the generate_targets python script

* increase TOTAL_TARGETS on jwt-hs loadtest

.github/workflows/test.yaml

@@ -113,7 +113,7 @@ jobs:
   loadtest:
     strategy:
       matrix:
-        kind: ['mixed', 'jwt-hs-50k', 'jwt-rsa-1k']
+        kind: ['mixed', 'jwt-hs', 'jwt-rsa']
     name: Loadtest
     runs-on: ubuntu-24.04
     steps: