nix(loadtest): move errors into mixed

Because we separate loadtest results per URL now, we can move the error
tests into the regular mixed bag of loadtests - we will be able to tell
from the misspelled URLs when we hit a regression in that area.

We should be able to do similar things for JWT tests, but we'll need
more infrastructure here.

.github/workflows/test.yaml

@@ -127,7 +127,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        kind: ['mixed', 'errors', 'jwt-hs', 'jwt-hs-cache', 'jwt-hs-cache-worst', 'jwt-rsa', 'jwt-rsa-cache', 'jwt-rsa-cache-worst']
+        kind: ['mixed', 'jwt-hs', 'jwt-hs-cache', 'jwt-hs-cache-worst', 'jwt-rsa', 'jwt-rsa-cache', 'jwt-rsa-cache-worst']
     name: Loadtest
     runs-on: ubuntu-24.04
     steps: