Change Bootstrap Styles to ^1.2.0 for the Bootstrap Layout Builder 2.2.x branch to work with Drupal ^10.3 || ^11

Problem/Motivation

#3474702: Change the 2.1.x branch to support Drupal < 10.3 for a smoother update process
#3429050: Automated Drupal 11 compatibility fixes for bootstrap_layout_builder
#3474611: Change to require at least Drupal 10.3

Proposed resolution

Change drupal/bootstrap_styles to ^1.2.0 in the composer.json file.

Remaining tasks

User interface changes

API changes

Data model changes