Fix rubocop convention offenses

While we use Pronto to detect offenses in the lines changed in our pull
request, sometimes our changes introduce offenses in other lines, and we
don't detect them.

In commit 0488b3735, we removed the only usage of the `heading` method
in a test, which caused a `RSpec/LetSetup` offense.

In commit 287c48873, we changed some lines from `fill_in` to
`fill_in_ckeditor`. Some of these lines were aligned with the following
ones, which after that change had extra spacing for no reason.

Finally, in commit 8d38ed58c we added a line before two lines which had
their equals signs aligned. Since, after adding this line, the block was
no longer aligned, there was no reason for the extra space in one of the
lines.

spec/system/emails_spec.rb

@@ -344,7 +344,7 @@ describe "Emails" do
   context "Budgets" do
     let(:author) { create(:user, :level_two) }
     let(:budget) { create(:budget) }
-    let!(:heading) { create(:budget_heading, name: "More hospitals", budget: budget) }
+    before { create(:budget_heading, name: "More hospitals", budget: budget) }
 
     scenario "Investment created" do
       login_as(author)