Fix failing tests

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

tests/acls/acl_policy_basic_groups.hujson

@@ -3,7 +3,7 @@
 {
     "groups": {
         "group:example": [
-            "testnamespace",
+            "testuser",
         ],
     },
 
@@ -23,4 +23,4 @@
             ],
         },
     ],
-}
+}

tests/acls/acl_policy_basic_user_as_user.hujson

@@ -10,11 +10,11 @@
         {
             "action": "accept",
             "src": [
-                "testnamespace",
+                "testuser",
             ],
             "dst": [
                 "host-1:*",
             ],
         },
     ],
-}
+}