Fix RSpec/ContextWording cop (#24739)

spec/models/email_domain_block_spec.rb

@@ -6,7 +6,7 @@ RSpec.describe EmailDomainBlock, type: :model do
   describe 'block?' do
     let(:input) { nil }
 
-    context 'given an e-mail address' do
+    context 'when given an e-mail address' do
       let(:input) { "foo@#{domain}" }
 
       context do
@@ -33,7 +33,7 @@ RSpec.describe EmailDomainBlock, type: :model do
       end
     end
 
-    context 'given an array of domains' do
+    context 'when given an array of domains' do
       let(:input) { %w(foo.com mail.foo.com) }
 
       it 'returns true if the domain is blocked' do