Move the rest of the marketing margin utilities to primer core, and remove marketing/margin.scss completely

Author: tobiasahlin

src/marketing/utilities/index.scss

@@ -4,4 +4,3 @@
 @import "./borders.scss";
 @import "./filters.scss";
 @import "./layout.scss";
-@import "./margin.scss";

src/marketing/utilities/margin.scss

@@ -59,3 +59,7 @@
     }
   }
 }
+
+.m-auto { margin: auto !important; }
+
+.mt-auto { margin-top: auto !important; }