Run Starlark tests only with Python 3

The macro `py2and3_strict_test` was generating twice as many tests, but we don't need them.

RELNOTES: None.
PiperOrigin-RevId: 318835824
diff --git a/src/test/starlark/BUILD b/src/test/starlark/BUILD
index 98b0dda..f1555b6 100644
--- a/src/test/starlark/BUILD
+++ b/src/test/starlark/BUILD
@@ -1,4 +1,3 @@
-load("//tools/python:private/py_test_alias.bzl", "py_test_alias")
 load(
     "//tools/build_rules:test_rules.bzl",
     "file_test",
@@ -14,7 +13,7 @@
 )
 
 [
-    py_test_alias(
+    py_test(
         name = "starlark_test_" + test_file.replace(".", "_"),
         srcs = [
             "starlark_test.py",
@@ -26,6 +25,7 @@
             test_file,
         ],
         main = "starlark_test.py",
+        python_version = "PY3",
     )
     for test_file in glob(["testdata/*"])
 ]