fixtures: remove a no longer needed sort

Dicts these days preserve order, so the sort is no longer needed to
achieve determinism.

As shown by the `test_dynamic_parametrized_ordering` test, this can
change the ordering of items, but only in equivalent ways (same number
of setups/teardowns per scope), it will just respect the user's given
ordering better (hence `vxlan` items now ordered before `vlan` items
compared to the previous ordering).

src/_pytest/fixtures.py

@@ -172,10 +172,7 @@ def get_parametrized_fixture_keys(
         callspec: CallSpec2 = item.callspec  # type: ignore[attr-defined]
     except AttributeError:
         return
-    # cs.indices is random order of argnames.  Need to
-    # sort this so that different calls to
-    # get_parametrized_fixture_keys will be deterministic.
-    for argname in sorted(callspec.indices):
+    for argname in callspec.indices:
         if callspec._arg2scope[argname] != scope:
             continue
 

testing/python/fixtures.py

@@ -2730,12 +2730,12 @@ def test2(reprovision):
             """
             test_dynamic_parametrized_ordering.py::test[flavor1-vxlan] PASSED
             test_dynamic_parametrized_ordering.py::test2[flavor1-vxlan] PASSED
-            test_dynamic_parametrized_ordering.py::test[flavor2-vxlan] PASSED
-            test_dynamic_parametrized_ordering.py::test2[flavor2-vxlan] PASSED
-            test_dynamic_parametrized_ordering.py::test[flavor2-vlan] PASSED
-            test_dynamic_parametrized_ordering.py::test2[flavor2-vlan] PASSED
             test_dynamic_parametrized_ordering.py::test[flavor1-vlan] PASSED
             test_dynamic_parametrized_ordering.py::test2[flavor1-vlan] PASSED
+            test_dynamic_parametrized_ordering.py::test[flavor2-vlan] PASSED
+            test_dynamic_parametrized_ordering.py::test2[flavor2-vlan] PASSED
+            test_dynamic_parametrized_ordering.py::test[flavor2-vxlan] PASSED
+            test_dynamic_parametrized_ordering.py::test2[flavor2-vxlan] PASSED
         """
         )