stylelint: Update deprecated at-import-partial-extension

It is spelled "load-partial-extension" now.

https://github.com/stylelint-scss/stylelint-config-recommended-scss/releases/tag/v14.1.0

.stylelintrc.json

@@ -23,7 +23,7 @@
 	"no-descending-specificity": null,
 	"no-duplicate-selectors": null,
 	"scss/at-extend-no-missing-placeholder": null,
-	"scss/at-import-partial-extension": null,
+	"scss/load-partial-extension": null,
 	"scss/at-import-no-partial-leading-underscore": null,
 	"scss/load-no-partial-leading-underscore": true,
 	"scss/at-mixin-pattern": null,