Remove default value for 'mode' in CLI options

Setting a default value will override the defaults in Configuration, which reads from the SOLID_QUEUE_SUPERVISOR_MODE environment variable, effectively making it useless

Author: lovro-bikic

lib/solid_queue/cli.rb

@@ -8,7 +8,7 @@ class Cli < Thor
       desc: "Path to config file (default: #{Configuration::DEFAULT_CONFIG_FILE_PATH}).",
       banner: "SOLID_QUEUE_CONFIG"
 
-    class_option :mode, type: :string, default: "fork", enum: %w[ fork async ],
+    class_option :mode, type: :string, enum: %w[ fork async ],
       desc: "Whether to fork processes for workers and dispatchers (fork) or to run these in the same process as the supervisor (async) (default: fork).",
       banner: "SOLID_QUEUE_SUPERVISOR_MODE"