tests/problems: adjust test code for oldestSupportedRelease=26.05 & fix maintainerless kind error in the same domain (#540341)

doc/release-notes/rl-2611.section.md

@@ -142,10 +142,11 @@
 
 ### Deprecations {#sec-nixpkgs-release-26.11-lib-deprecations}
 
-- Create the first release note entry in this section!
+- Setting `config.allowBrokenPredicate` is deprecated in favor of
+  using `config.problems.handlers.PackageName.broken = "warn"` (or `=
+  "ignore"`). For more information see [](#sec-allow-broken).
 
 
 ### Additions and Improvements {#sec-nixpkgs-release-26.11-lib-additions-improvements}
 
 - Create the first release note entry in this section!
-

pkgs/test/problems/cases/allow-broken-predicate-match/default.nix

@@ -5,7 +5,7 @@ let
     system = "x86_64-linux";
     overlays = [ ];
     config = {
-      allowBrokenPredicate = attrs: lib.getName attrs == "a";
+      problems.handlers.a.broken = "ignore";
     };
   };
 in

pkgs/test/problems/cases/invalid-kind-error/expected-stderr

@@ -1,4 +1,4 @@
 (stack trace truncated; use '--show-trace' to show the full, detailed trace)
 
 error: Refusing to evaluate package 'a-0' in /nix/store/eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee-default.nix:11 because it has an invalid meta attrset:
-  - a.meta.problems.invalid: Problem kind invalid, inferred from the problem name, is invalid; expected enum<broken,deprecated,removal>. You can specify an explicit problem kind with `a.meta.problems.invalid.kind`
+  - a.meta.problems.invalid: Problem kind invalid, inferred from the problem name, is invalid; expected enum<broken,deprecated,maintainerless,removal>. You can specify an explicit problem kind with `a.meta.problems.invalid.kind`