vulns: raise let-free spec files to typed: strict

utils/repology_spec, identify_spec and purl_spec go to typed: strict
with sigs added on their helper methods. cpan_sec_spec, vulns/repology_spec,
match_spec and dev-cmd/advisory-match_spec stay at typed: true because
they use let, which generates a sig-less method that strict rejects (no
brew spec at typed: strict uses let).

Library/Homebrew/test/utils/repology_spec.rb

@@ -1,4 +1,4 @@
-# typed: true
+# typed: strict
 # frozen_string_literal: true
 
 require "utils/repology"
@@ -10,6 +10,10 @@ RSpec.describe Repology do
   end
 
   describe ".single_package_query" do
+    sig {
+      params(success: T::Boolean, stdout: String, stderr: String, exit_status: Integer)
+        .returns(T.untyped)
+    }
     def stub_curl(success:, stdout: "", stderr: "", exit_status: 0)
       instance_double(SystemCommand::Result, success?: success, stdout:, stderr:, exit_status:)
     end

Library/Homebrew/test/vulns/identify_spec.rb

@@ -1,4 +1,4 @@
-# typed: true
+# typed: strict
 # frozen_string_literal: true
 
 require "vulns/identify"
@@ -146,6 +146,7 @@ RSpec.describe Homebrew::Vulns::Identify do
   end
 
   describe ".registry_package" do
+    sig { params(url: T.nilable(String)).returns(T.nilable(T::Hash[Symbol, T.untyped])) }
     def result(url)
       described_class.registry_package(url)&.to_h
     end

Library/Homebrew/test/vulns/purl_spec.rb

@@ -1,4 +1,4 @@
-# typed: true
+# typed: strict
 # frozen_string_literal: true
 
 require "vulns/purl"