[TASK] Switch to a fixed version for xdebug (the latest one requires PHP 7.3)

recipes/default.rb

@@ -23,7 +23,10 @@
 # THE SOFTWARE.
 
 if node['platform_version'] == '16.04'
-	package 'php-xdebug'
+	package 'php-xdebug' do
+		version ['2.4.0-1']
+	end
+
 
 	template '/etc/php/' + node['ubuntu_base']['php_version'] + '/apache2/conf.d/xdebug.ini' do
 		mode '0644'