Remove unnecessary class names in relations

Just like we do in the Budget module, and in some places in the Poll and
Legislation modules, we don't need to specify the class name when the
name of the relation matches the name of a class in the same module.

app/models/poll/ballot.rb

@@ -1,5 +1,5 @@
 class Poll::Ballot < ApplicationRecord
-  belongs_to :ballot_sheet, class_name: "Poll::BallotSheet"
+  belongs_to :ballot_sheet
 
   validates :ballot_sheet_id, presence: true
 

app/models/poll/ballot_sheet.rb

@@ -1,7 +1,7 @@
 class Poll::BallotSheet < ApplicationRecord
   belongs_to :poll
   belongs_to :officer_assignment
-  has_many :ballots, class_name: "Poll::Ballot"
+  has_many :ballots
 
   validates :data, presence: true
   validates :poll_id, presence: true

app/models/poll/booth.rb

@@ -1,6 +1,6 @@
 class Poll
   class Booth < ApplicationRecord
-    has_many :booth_assignments, class_name: "Poll::BoothAssignment"
+    has_many :booth_assignments
     has_many :polls, through: :booth_assignments
     has_many :shifts
 

app/models/poll/booth_assignment.rb

@@ -5,7 +5,7 @@ class Poll
 
     before_destroy :destroy_poll_shifts, only: :destroy
 
-    has_many :officer_assignments, class_name: "Poll::OfficerAssignment", dependent: :destroy
+    has_many :officer_assignments, dependent: :destroy
     has_many :officers, through: :officer_assignments
     has_many :voters
     has_many :partial_results

app/models/poll/officer.rb

@@ -1,8 +1,8 @@
 class Poll
   class Officer < ApplicationRecord
     belongs_to :user
-    has_many :officer_assignments, class_name: "Poll::OfficerAssignment"
-    has_many :shifts, class_name: "Poll::Shift"
+    has_many :officer_assignments
+    has_many :shifts
     has_many :failed_census_calls, foreign_key: :poll_officer_id
 
     validates :user_id, presence: true, uniqueness: true

app/models/poll/question.rb

@@ -15,7 +15,7 @@ class Poll::Question < ApplicationRecord
   has_many :answers, class_name: "Poll::Answer"
   has_many :question_answers, -> { order "given_order asc" }, class_name: "Poll::Question::Answer", dependent: :destroy
   has_many :partial_results
-  has_many :pair_answers, class_name: "Poll::PairAnswer"
+  has_many :pair_answers
   has_one :votation_type, as: :questionable
   belongs_to :proposal