fix(build): upgrade css minify and remove specialcomments

This PR upgrades gulp-clean-css (respectively clean-css) to the latest version.
Now the removement of special header comments in the concatenated minified css file semantic.min.css is properly done and works
Before, the minified concatenated css file still contained every special /*! ... */ header from each single .css file which increased the minified css file significantly.

package.json

@@ -43,7 +43,7 @@
     "gulp": "^4.0.0",
     "gulp-autoprefixer": "^6.0.0",
     "gulp-chmod": "^2.0.0",
-    "gulp-clean-css": "^3.10.0",
+    "gulp-clean-css": "^4.3.0",
     "gulp-clone": "^2.0.1",
     "gulp-concat": "^2.6.1",
     "gulp-concat-css": "^3.1.0",

tasks/config/tasks.js

@@ -143,10 +143,11 @@ module.exports = {
 
     /* Minified CSS Concat */
     minify: {
-      processImport       : false,
-      restructuring       : false,
-      keepSpecialComments : 1,
-      roundingPrecision   : -1,
+      level: {
+        1: {
+          inline          : false
+        }
+      }
     },
 
     /* Minified JS Settings */
@@ -159,10 +160,12 @@ module.exports = {
 
     /* Minified Concat CSS Settings */
     concatMinify: {
-      processImport       : false,
-      restructuring       : false,
-      keepSpecialComments : false,
-      roundingPrecision   : -1,
+      level: {
+        1: {
+          inline          : false,
+          specialComments : false
+        }
+      }
     },
 
     /* Minified Concat JS */