Fix grammar (#20106)

spec/models/account_spec.rb

@@ -755,7 +755,7 @@ RSpec.describe Account, type: :model do
         expect(account).to model_have_error_on_field(:username)
       end
 
-      it 'is invalid if the username is longer then 30 characters' do
+      it 'is invalid if the username is longer than 30 characters' do
         account = Fabricate.build(:account, username: Faker::Lorem.characters(number: 31))
         account.valid?
         expect(account).to model_have_error_on_field(:username)
@@ -801,7 +801,7 @@ RSpec.describe Account, type: :model do
         expect(account).to model_have_error_on_field(:username)
       end
 
-      it 'is valid even if the username is longer then 30 characters' do
+      it 'is valid even if the username is longer than 30 characters' do
         account = Fabricate.build(:account, domain: 'domain', username: Faker::Lorem.characters(number: 31))
         account.valid?
         expect(account).not_to model_have_error_on_field(:username)