Don't call check_all_pending! for older Rails

Author: andyw8

lib/ruby_lsp/ruby_lsp_rails/server.rb

@@ -259,7 +259,8 @@ def active_record_model?(const)
       end
 
       def pending_migrations_message
-        return unless defined?(ActiveRecord)
+        # `check_all_pending!` is only available since Rails 7.1
+        return unless defined?(ActiveRecord) && ActiveRecord::Migration.respond_to?(:check_all_pending!)
 
         ActiveRecord::Migration.check_all_pending!
         nil