Replace gulp with plain npm for linting.

assets/sass/base/document/_document.scss

@@ -1,4 +1,4 @@
-// sass-lint:disable no-vendor-prefixes
+// stylelint-disable property-no-vendor-prefix
 
 // Document
 //

assets/sass/base/forms/_forms.scss

@@ -1,4 +1,4 @@
-// sass-lint:disable no-vendor-prefixes, no-css-comments
+// stylelint-disable property-no-vendor-prefix
 
 // Form defaults
 //

assets/sass/base/links/_links.scss

@@ -14,7 +14,7 @@
 a,
 %link {
   color: $link;
-  // sass-lint:disable no-vendor-prefixes
+  // stylelint-disable property-no-vendor-prefix
   // Remove gaps in links underline in iOS 8+ and Safari 8+.
   -webkit-text-decoration-skip: objects;
 }

assets/sass/base/text/_text.scss

@@ -10,7 +10,7 @@
 abbr[title] {
   // Remove the bottom border in Chrome 57- and Firefox 39-.
   border-bottom: 0;
-  // sass-lint:disable no-duplicate-properties
+  // stylelint-disable no-duplicate-properties
   // Add the correct text decoration in Chrome, Edge, IE, Opera, and Safari.
   text-decoration: underline;
   text-decoration: underline dotted;
@@ -31,7 +31,7 @@ strong {
   font-weight: inherit;
 }
 
-// sass-lint:disable no-mergeable-selectors
+// stylelint-disable no-mergeable-selectors
 b,
 strong {
   // Add the correct font weight in Chrome, Edge, and Safari.