UHF-8714: Change the sidebar text block background color to gray

[teroelonen]

UHF-8714

What was done

• Changed the sidebar text block background color to gray.

How to install

• Make sure your instance is up and running on latest dev branch.
  • git pull origin dev
  • make fresh
• Update the HDBT theme
  • composer require drupal/hdbt:dev-UHF-8714_change_sidebar_background_color
• Run make drush-cr

How to test

• Go to any standard page or TPR unit or TPR service and add content to sidebar. Select the text block and paste the html-dom that is linked below.
• Check that all the elements have gray background now instead of the secondary colors that were coming from the color palette before.
• Check that code follows our standards

Designers review

• This PR does not need designers review
• This PR has been visually reviewed by a designer (Name of the designer)

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