Add and apply rubocop rules for empty lines

We were very inconsistent regarding these rules.

Personally I prefer no empty lines around blocks, clases, etc... as
recommended by the Ruby style guide [1], and they're the default values
in rubocop, so those are the settings I'm applying.

The exception is the `private` access modifier, since we were leaving
empty lines around it most of the time. That's the default rubocop rule
as well. Personally I don't have a strong preference about this one.


[1] https://rubystyle.guide/#empty-lines-around-bodies

spec/models/poll/question_spec.rb

@@ -47,7 +47,6 @@ RSpec.describe Poll::Question, type: :model do
   end
 
   describe "#enum_type" do
-
     it "returns nil if not has votation_type association" do
       expect(poll_question.votation_type).to be_nil
       expect(poll_question.enum_type).to be_nil
@@ -59,11 +58,9 @@ RSpec.describe Poll::Question, type: :model do
       expect(question.votation_type).not_to be_nil
       expect(question.enum_type).to eq("answer_couples_open")
     end
-
   end
 
   describe "#max_votes" do
-
     it "returns nil if not has votation_type association" do
       expect(poll_question.votation_type).to be_nil
       expect(poll_question.max_votes).to be_nil
@@ -75,6 +72,5 @@ RSpec.describe Poll::Question, type: :model do
       expect(question.votation_type).not_to be_nil
       expect(question.max_votes).to eq(5)
     end
-
   end
 end