fix(harness): drop THOTH_SSL_CA from REQUIRED_L2 + isolate profile in workspace test

Two fixes found while unblocking the L2 setup:

1. conftest: THOTH_SSL_CA is NOT an L2 prerequisite. The DWH endpoint presents a
   public cert (*.policlinicosandonato.it, signed by GoDaddy), already in the
   certifi bundle, so the REST clients validate TLS with verify=True -- no CA file
   needed. The ssl_ca line was commented out in ChironeWp3's nsp.yaml too.

2. test_workspace: the profile-default assertion collided with the operator's real
   harness/.env once load_dotenv (D3) started injecting THOTH_PROFILE into the
   process env. The test now dels THOTH_PROFILE to assert the actual *default*
   (server), regardless of what the operator set in .env.

Suite: 109 passed.

harness/tests/test_workspace.py

@@ -4,6 +4,10 @@ from nsp.workspace import load_workspace, WorkspaceError
 
 
 def test_load_workspace_expands_env_vars(monkeypatch, tmp_path):
+    # Isolate profile: load_dotenv (conftest D3) injects THOTH_PROFILE from the real
+    # harness/.env into os.environ; this test asserts the *default* (server), so it
+    # must del THOTH_PROFILE rather than inherit whatever the operator set.
+    monkeypatch.delenv("THOTH_PROFILE", raising=False)
     monkeypatch.setenv("THOTH_VEC_API_KEY", "secret-reader")
     monkeypatch.setenv("THOTH_VEC_WRITE_API_KEY", "secret-writer")
     monkeypatch.setenv("THOTH_VEC_REST_URL", "https://example/vector/v1/")