Drupal11 fixes

1. Minor changes

   • Removed unused variables: $first_submission and $column_headers
   • Fixed phpcs issue "Parameter $account has null default value, but is not marked as nullable."
   • Fixed phpcs issue "Line exceeds 80 characters" of README.md file

2. Composer installation failed for Drupal 11 with below error.

Your requirements could not be resolved to an installable set of packages.

Problem 1

- drupal/complete_webform_exporter[1.0.0, ..., 1.0.2] require drupal/webform ^6 -> satisfiable by drupal/webform[6.0.0, ..., 6.2.9].

- drupal/webform[6.0.0, ..., 6.1.4] require drupal/core ^8.8 || ^9 -> found drupal/core[8.8.0, ..., 8.9.20, 9.0.0, ..., 9.5.11] but the package is fixed to 11.1.1 (lock file version) by a partial update and that version does not match. Make sure you list it as an argument for the update command.

- drupal/webform[6.1.5, ..., 6.1.8] require drupal/core ^9.3 -> found drupal/core[9.3.0, ..., 9.5.11] but the package is fixed to 11.1.1 (lock file version) by a partial update and that version does not match. Make sure you list it as an argument for the update command.

- drupal/webform[6.2.0, ..., 6.2.6] require drupal/core ^9.4 || ^10 -> found drupal/core[9.4.0, ..., 9.5.11, 10.0.0, ..., 10.4.1] but the package is fixed to 11.1.1 (lock file version) by a partial update and that version does not match. Make sure you list it as an argument for the update command.

- drupal/webform[6.2.5, ..., 6.2.7] require drupal/core ^10.1 -> found drupal/core[10.1.0, ..., 10.4.1] but the package is fixed to 11.1.1 (lock file version) by a partial update and that version does not match. Make sure you list it as an argument for the update command.

- drupal/webform[6.2.8, ..., 6.2.9] require drupal/core ^10.2 -> found drupal/core[10.2.0, ..., 10.4.1] but the package is fixed to 11.1.1 (lock file version) by a partial update and that version does not match. Make sure you list it as an argument for the update command.

- Root composer.json requires drupal/complete_webform_exporter ^1.0 -> satisfiable by drupal/complete_webform_exporter[1.0.0, 1.0.1, 1.0.2].