Fix lit_autoupdate for explorer (#2801)

#2793 added a README.md, #2796 added the non-auto-updated test.

bazel/testing/lit_autoupdate_base.py

@@ -152,7 +152,7 @@ def get_tests(testdata: str) -> Set[Path]:
     tests = set()
     for root, _, files in os.walk(testdata):
         for f in files:
-            if f in {"lit.cfg.py", "BUILD"}:
+            if f in {"lit.cfg.py", "BUILD", "README.md"}:
                 # Ignore the lit config.
                 continue
             if os.path.splitext(f)[1] == ".carbon":

explorer/testdata/alias/interface_method_as_class_member.carbon → explorer/testdata/alias/fail_interface_method_as_class_member.carbon

@@ -35,7 +35,7 @@ impl forall [U:! Printable] Vector(U) as Printable {
 
 fn Main() -> i32 {
   var v: Vector(String) = {.x = "test"};
-  // CHECK:STDERR: COMPILATION ERROR: {{.*}}/explorer/testdata/alias/interface_method_as_class_member.carbon:[[@LINE+1]]: Member access to aliases is not yet supported.
+  // CHECK:STDERR: COMPILATION ERROR: {{.*}}/explorer/testdata/alias/fail_interface_method_as_class_member.carbon:[[@LINE+1]]: Member access to aliases is not yet supported.
   v.PrintIt();
   return 42;
 }