Fix two rogue messages on tests

These two messages would appear on some tests, on the console. With
this commit those messages are still caught but don’t show up on the
console anymore (in the middle of RSpec’s dots).

The messages were:
- You have to provide an email address. Usage: rake member:delete'[[email protected]]'
- Checking for expected text of nil is confusing and/or pointless since it will always
  match. Please specify a string or regexp instead.

Technically, the second one is not a message we display on the code,
but rather an RSpec warning telling us one of our variables was nil.
Adding content to the constructor was the solution.

spec/fabricators/sponsor_fabricator.rb

@@ -15,6 +15,7 @@
 Fabricator(:sponsor_full, from: :sponsor) do
   description { Faker::Lorem.word }
   level { 'gold' }
+  accessibility_info { 'Accessible parking spaces' }
 end
 
 Fabricator(:sponsor_with_member_contacts, from: :sponsor) do

spec/lib/tasks/delete_member_rake_spec.rb

@@ -11,7 +11,9 @@
   end
 
   it 'when no email is provided' do
-    expect { task.invoke }.to raise_error(SystemExit, "You have to provide an email address. Usage: rake member:delete'[[email protected]]'")
+    regexed_msg = Regexp.quote("You have to provide an email address. Usage: rake member:delete'[[email protected]]'")
+    expect { task.invoke }.to output(/#{regexed_msg}\s*/).to_stderr
+      .and raise_error(SystemExit)
   end
 
   it 'anonymises member information' do