Removes sed command from Dockerfile

[efremovd]

They were needed before because they changed example config.php to make it workable. Now we don't have it and running sed against main php file just removes a lot of code and forces data path for directory

Example of changes before sed:

// clean and check $root_path
$root_path = rtrim($root_path, '\\/');
$root_path = str_replace('\\', '/', $root_path);
if (!@is_dir($root_path)) {
    echo "<h1>".lng('Root path')." \"{$root_path}\" ".lng('not found!')." </h1>";
    exit;
}

becomes after sed:

$root_path = $_SERVER['DOCUMENT_ROOT'].'/data';
$root_path = $_SERVER['DOCUMENT_ROOT'].'/data';
if (!@is_dir($root_path)) {
    echo "<h1>".lng('Root path')." \"{$root_path}\" ".lng('not found!')." </h1>";
    exit;
}

thus forcing data as a path and ignores whatever what set in config.php