Fix Ruby 2.7 deprecation warnings in migration helpers

Per https://www.ruby-lang.org/en/news/2019/12/25/ruby-2-7-0-released/,
the automatic conversion of keyword arguments and positional arguments
is deprecated. Now we have to be explicit about the differences.

lib/gitlab/database/migration_helpers.rb

@@ -176,7 +176,7 @@ module Gitlab
           name: name.presence || concurrent_foreign_key_name(source, column)
         }
 
-        if foreign_key_exists?(source, target, options)
+        if foreign_key_exists?(source, target, **options)
           warning_message = "Foreign key not created because it exists already " \
             "(this may be due to an aborted migration or similar): " \
             "source: #{source}, target: #{target}, column: #{options[:column]}, "\
@@ -330,13 +330,13 @@ module Gitlab
       # * +timing_configuration+ - [[ActiveSupport::Duration, ActiveSupport::Duration], ...] lock timeout for the block, sleep time before the next iteration, defaults to `Gitlab::Database::WithLockRetries::DEFAULT_TIMING_CONFIGURATION`
       # * +logger+ - [Gitlab::JsonLogger]
       # * +env+ - [Hash] custom environment hash, see the example with `DISABLE_LOCK_RETRIES`
-      def with_lock_retries(**args, &block)
+      def with_lock_retries(*args, **kwargs, &block)
         merged_args = {
           klass: self.class,
           logger: Gitlab::BackgroundMigration::Logger
-        }.merge(args)
+        }.merge(kwargs)
 
-        Gitlab::Database::WithLockRetries.new(merged_args).run(&block)
+        Gitlab::Database::WithLockRetries.new(**merged_args).run(&block)
       end
 
       def true_value