refactor(dialog): update fluent content typography style

Author: desig9stein

projects/igniteui-angular/src/lib/core/styles/typography/_fluent.scss

@@ -61,7 +61,10 @@
     ));
     @include column-actions-typography();
     @include date-range-typography();
-    @include dialog-typography();
+    @include dialog-typography($categories: (
+        title: 'h6',
+        content: 'body-2'
+    ));
     @include dock-manager-typography();
     @include drop-down-typography();
     @include expansion-panel-typography($categories: (