Remove no longer used .sass-lint.yml

Changelog-entry: Remove no longer used .sass-lint.yml
Change-type: patch

.sass-lint.yml

@@ -1,17 +0,0 @@
-# sass-lint config generated by make-sass-lint-config v0.1.2
-
-files:
-  include: lib/gui/scss/**/*.scss
-options:
-  formatter: stylish
-  merge-default-rules: false
-rules:
-  no-css-comments: 0
-  no-important: 0
-  no-qualifying-elements: 0
-  placeholder-in-extend: 0
-  property-sort-order: 0
-  quotes:
-    - 1
-    - style: double
-