Bump rubocop-rails from 2.20.2 to 2.21.2

Bumps [rubocop-rails](https://github.com/rubocop/rubocop-rails) from 2.20.2 to 2.21.2.
- [Release notes](https://github.com/rubocop/rubocop-rails/releases)
- [Changelog](https://github.com/rubocop/rubocop-rails/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop/rubocop-rails/compare/v2.20.2...v2.21.2)

---
updated-dependencies:
- dependency-name: rubocop-rails
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Note version 2.21.0 relaxes the default `Include` path for
`Rails/FindEach`, and so this version can find and correct offenses
outside the `app/models/` folder [1].

Also note this version replaces `unless something.include?` with `if
something.exclude?`; since we don't use the `exclude?` method anywhere,
we're removing the `include?` method from the list of methods checked by
this cop.

Finally, the Rails/HttpStatus method now returns a false positive when
rendering a dashboard partial and passing the `status` variable. In
order to avoid this issue, we could change the name of the local
variable or move the partial to a component, but for now we're simply
excluding these files for this cop.

[1] https://github.com/rubocop/rubocop-rails/pull/1059/commits/0066b3505

Signed-off-by: dependabot[bot] <support@github.com>

db/dev_seeds/budgets.rb

@@ -48,7 +48,7 @@ section "Creating Budgets" do
     end
   end
 
-  Budget.all.each do |budget|
+  Budget.all.find_each do |budget|
     city_group = budget.groups.create!(
       random_locales_attributes(name: -> { I18n.t("seeds.budgets.groups.all_city") })
     )

db/dev_seeds/polls.rb

@@ -102,7 +102,7 @@ end
 
 section "Creating Poll Shifts for Poll Officers" do
   Poll.find_each do |poll|
-    Poll::BoothAssignment.where(poll: poll).each do |booth_assignment|
+    Poll::BoothAssignment.where(poll: poll).find_each do |booth_assignment|
       scrutiny = (poll.ends_at.to_datetime..poll.ends_at.to_datetime + Poll::RECOUNT_DURATION)
       Poll::Officer.find_each do |poll_officer|
         {

db/dev_seeds/sdg.rb

@@ -32,7 +32,7 @@ section "Creating Sustainable Development Goals" do
 end
 
 section "Creating SDG homepage cards" do
-  SDG::Phase.all.each do |phase|
+  SDG::Phase.all.find_each do |phase|
     Widget::Card.create!(cardable: phase, title: "#{phase.title} card",
                          link_text: "Link Text", link_url: "/any_path")
   end