Chore: RuboCop Style/MultipleComparison

This fixes the single instance of the offense for MultipleComparison.
It turned out that the code wasn't needed at all, since
`Faraday::Utils.escape` already correctly stringifies booleans.

I also added a unit test that seemed to be missing for this code.

.rubocop_todo.yml

@@ -1,6 +1,6 @@
 # This configuration was generated by
 # `rubocop --auto-gen-config`
-# on 2019-03-04 02:27:02 +0900 using RuboCop version 0.65.0.
+# on 2019-03-04 10:37:51 +0800 using RuboCop version 0.65.0.
 # The point is for the user to remove these configuration records
 # one by one as the offenses are removed from the code base.
 # Note that changes in the inspected code, or installation of new
@@ -135,11 +135,6 @@ Style/MultilineIfModifier:
     - 'test/adapters/em_http_test.rb'
     - 'test/helper.rb'
 
-# Offense count: 1
-Style/MultipleComparison:
-  Exclude:
-    - 'lib/faraday/encoders/flat_params_encoder.rb'
-
 # Offense count: 11
 # Cop supports --auto-correct.
 # Configuration parameters: EnforcedStyle.

lib/faraday/encoders/flat_params_encoder.rb

@@ -29,7 +29,6 @@ def self.encode(params)
       buffer = +''
       params.each do |key, value|
         encoded_key = escape(key)
-        value = value.to_s if value == true || value == false
         if value.nil?
           buffer << "#{encoded_key}&"
         elsif value.is_a?(Array)

spec/faraday/params_encoders/flat_spec.rb

@@ -10,4 +10,10 @@
     expected = { 'a' => %w[one two three] }
     expect(subject.decode(query)).to eq(expected)
   end
+
+  it 'decodes boolean values' do
+    query = 'a=true&b=false'
+    expected = { 'a' => 'true', 'b' => 'false' }
+    expect(subject.decode(query)).to eq(expected)
+  end
 end