Scss Mixed Declarations Warnings

## Loads of scss deprecation warnings in the console - making it pretty busy and harder to spot any other unrelated errors

```
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

╷
92 │ ┌ .apos-theme--primary-blue {
93 │ │ @include apos-primary-mixin(#0062ff);
94 │ │ }
│ └─── nested rule
... │
96 │ --a-base-1: #d1d3d5;
│ ^^^^^^^^^^^^^^^^^^^ declaration
╵
apos-build/default/apos/modules/@apostrophecms/ui/scss/global/_theme.scss 96:3 @import
apos-build/default/apos/modules/@apostrophecms/ui/scss/global/import-all.scss 11:9 root stylesheet
```

So I'm wondering if there's a fix to mute these warnings and/or if the Apostrophe team are planning to opt-in with the new behaviour and then release updated global scss files?

Thanks

Start with apos-build/default/apos/modules/@apostrophecms/ui/scss/global/_theme.scss around lines 92-96 and its import from import-all.scss at line 11, then trace these generated paths to the source SCSS. Reproduce the Sass build and determine the intended warning-handling change; done means the mixed-declarations warnings no longer obscure other errors without changing the theme behavior.

Written by the indexing model from the issue text.