Replace hardcoded colors with variables

[lopadz]

Description

While styling the admin app, I encountered these hardcoded values that should be changed in the core to avoid using a complex CSS targeting technique.

Code to change

• webiny-js/packages/ui/src/AutoComplete/MultiAutoComplete.tsx

  Line 40 in 552f914

  borderBottom: "2px solid #fa5723",

• webiny-js/packages/ui/src/AutoComplete/MultiAutoComplete.tsx

  Line 131 in 552f914

  return <MaterialSpinner size={24} spinnerColor={"#fa5723"} spinnerWidth={2} visible />;

[brunozoric]

Resolved in 5.40.8