remove email campaigns factory and export it as a standard component

.changeset/cyan-ties-tease.md

@@ -0,0 +1,11 @@
+---
+"@comet/brevo-admin": major
+---
+
+Remove factory createEmailCampaignsPage
+
+The `EmailCampaignsPage` can now be used like this:
+
+```tsx
+<EmailCampaignsPage EmailCampaignContentBlock={EmailCampaignContentBlock} />
+```