Move isolated matchers into the specs that uses them

Library/Homebrew/test/cmd/info_spec.rb

@@ -5,6 +5,15 @@ require "cmd/info"
 require "cmd/shared_examples/args_parse"
 
 RSpec.describe "brew info" do
+  RSpec::Matchers.define :a_json_string do
+    match do |actual|
+      JSON.parse(actual)
+      true
+    rescue JSON::ParserError
+      false
+    end
+  end
+
   it_behaves_like "parseable arguments"
 
   it "prints as json with the --json=v1 flag", :integration_test do

Library/Homebrew/test/spec_helper.rb

@@ -304,16 +304,6 @@ end
 
 RSpec::Matchers.define_negated_matcher :not_to_output, :output
 RSpec::Matchers.alias_matcher :have_failed, :be_failed
-RSpec::Matchers.alias_matcher :a_string_containing, :include
-
-RSpec::Matchers.define :a_json_string do
-  match do |actual|
-    JSON.parse(actual)
-    true
-  rescue JSON::ParserError
-    false
-  end
-end
 
 # Match consecutive elements in an array.
 RSpec::Matchers.define :array_including_cons do |*cons|

Library/Homebrew/test/system_command_result_spec.rb

@@ -3,6 +3,8 @@
 require "system_command"
 
 RSpec.describe SystemCommand::Result do
+  RSpec::Matchers.alias_matcher :a_string_containing, :include
+
   subject(:result) do
     described_class.new([], output_array, instance_double(Process::Status, exitstatus: 0, success?: true),
                         secrets: [])