Rework modal header structure

src/app/components/SpaceAuthError.svelte

@@ -11,6 +11,8 @@
   import Modal from "@lib/components/Modal.svelte"
   import ModalBody from "@lib/components/ModalBody.svelte"
   import ModalHeader from "@lib/components/ModalHeader.svelte"
+  import ModalTitle from "@lib/components/ModalTitle.svelte"
+  import ModalSubtitle from "@lib/components/ModalSubtitle.svelte"
   import ModalFooter from "@lib/components/ModalFooter.svelte"
   import SpaceAccessRequest from "@app/components/SpaceAccessRequest.svelte"
   import {pushModal, clearModals} from "@app/util/modal"
@@ -42,12 +44,8 @@
 <Modal tag="form" onsubmit={preventDefault(requestAccess)}>
   <ModalBody>
     <ModalHeader>
-      {#snippet title()}
-        <div>Access Error</div>
-      {/snippet}
-      {#snippet info()}
-        <div>We couldn't connect you to this space.</div>
-      {/snippet}
+      <ModalTitle>Access Error</ModalTitle>
+      <ModalSubtitle>We couldn't connect you to this space.</ModalSubtitle>
     </ModalHeader>
     <p>
       We received an error from the relay indicating you don't have access to {displayRelayUrl(