Add Sidekiq size limiter default to fake settings

These are needed when running background migration specs because those
execute Sidekiq client middleware and these use FakeApplicationSettings
with empty DB attributes

app/models/application_setting_implementation.rb

@@ -146,6 +146,9 @@ module ApplicationSettingImplementation
         session_expire_delay: Settings.gitlab['session_expire_delay'],
         shared_runners_enabled: Settings.gitlab_ci['shared_runners_enabled'],
         shared_runners_text: nil,
+        sidekiq_job_limiter_mode: Gitlab::SidekiqMiddleware::SizeLimiter::Validator::COMPRESS_MODE,
+        sidekiq_job_limiter_compression_threshold_bytes: Gitlab::SidekiqMiddleware::SizeLimiter::Validator::DEFAULT_COMPRESSION_THRESHOLD_BYTES,
+        sidekiq_job_limiter_limit_bytes: Gitlab::SidekiqMiddleware::SizeLimiter::Validator::DEFAULT_SIZE_LIMIT,
         sign_in_text: nil,
         signup_enabled: Settings.gitlab['signup_enabled'],
         snippet_size_limit: 50.megabytes,