Remove global h2 css rule in favour of heading styles/components (#32969)

* Remove global h2 css rule in favour of heading styles/components

* Use Compound Heading in shared-components

and forbid hX elements

* Use Compound Heading in settings

add back margin to some legacy headings

* Tweak some headings

* Update screenshots

* Update screenshots

* Update snapshots

* Tweak .gitignore

* Update snapshots

* Iterate

* Update screenshots

* Update screenshots

* Update screenshot

apps/web/res/css/views/rooms/_NewRoomIntro.pcss

@@ -37,9 +37,8 @@ Please see LICENSE files in the repository root for full details.
     }
 
     > h2 {
-        margin-top: 24px;
-        font-size: $font-24px;
-        font-weight: var(--cpd-font-weight-semibold);
+        margin: var(--cpd-space-6x) 0 var(--cpd-space-4x);
+        font: var(--cpd-font-heading-md-semibold);
     }
 
     > p {