Fix Sass nested selector deprecation warnings in bootstrap 4.6.2

[jxjj]

More info: https://sass-lang.com/d/mixed-decls. They all look related to bootstrap 4, so it might be easiest to bump to latest bootstrap.

Example:

Deprecation Warning: Sass's behavior for declarations that appear after nested
rules will be changing to match the behavior specified by CSS in an upcoming
version. To keep the existing behavior, move the declaration above the nested
rule. To opt into the new behavior, wrap the declaration in `& {}`.

More info: https://sass-lang.com/d/mixed-decls

   ┌──> node_modules/.pnpm/[email protected][email protected][email protected]/node_modules/bootstrap/scss/_custom-forms.scss
415│       appearance: none;
   │       ^^^^^^^^^^^^^^^^ declaration
   ╵
   ┌──> node_modules/.pnpm/[email protected][email protected][email protected]/node_modules/bootstrap/scss/mixins/_transition.scss
21 │ ┌       @media (prefers-reduced-motion: reduce) {
22 │ │         transition: none;
23 │ │       }
   │ └─── nested rule