Upgrade bootstrap from 4.3.1 to 4.5.0

!1015 (merged) missed some layout files to upgrade bootstrap from 4.3.1 to 4.5.0 due to my mistake.

Deprecation checklist

• bg-gradient-variant (4.5)
• bg-variant() (4.4)
• nav-divider() (4.4)
• form-control-focus() (4.4)

Changelogs

• 4.5.0 https://blog.getbootstrap.com/2020/05/12/bootstrap-4-5-0/
• 4.4.0 https://blog.getbootstrap.com/2019/11/26/bootstrap-4-4-0/

Closes #814 (closed)

cf. !1015 (merged), !336 (merged), !999 (merged)