Compiling Sass code that uses CoreUI emits "deprecation warnings" for alert-variant() and avatar() mixins even if the code isn't used.

Steps to reproduce:

1. import coreui in a scss file. For example: @use '@coreui/coreui/scss/coreui'
2. Compile with Sass

The solution is to move the deprecation @include inside the css rule: the warning is then only emitted if the deprecated mixin is used. I will submit a PR shortly.

Sample output (Bitfocus Companion webui compilation):

transforming (1684) ../node_modules/lodash-es/_copySymbols.jsWarning: alert-variant() has been deprecated as of v4.3.0. It will be removed entirely in v6.0.0.
../../../@coreui/coreui/scss/mixins/_deprecate.scss 10:5 deprecate()
../../../@coreui/coreui/scss/mixins/_alert.scss 4:1 @forward
../../../@coreui/coreui/scss/_mixins.scss 28:1 @forward
../../../@coreui/coreui/scss/coreui.scss 8:1 @use
../../../../webui/src/scss/_variables.scss 9:1 @use
../../../../webui/src/App.scss 3:1 root stylesheet

Warning: avatar() has been deprecated as of v5.1.0. It will be removed entirely in v6.0.0.
../../../@coreui/coreui/scss/mixins/_deprecate.scss 10:5 deprecate()
../../../@coreui/coreui/scss/mixins/_avatar.scss 4:1 @forward
../../../@coreui/coreui/scss/_mixins.scss 29:1 @forward
../../../@coreui/coreui/scss/coreui.scss 8:1 @use
../../../../webui/src/scss/_variables.scss 9:1 @use
../../../../webui/src/App.scss 3:1 root stylesheet