Tweak the migration guide formatting

- so that the list is displayed correctly

documentation/src/main/asciidoc/migration/index.adoc

@@ -45,6 +45,7 @@ Hibernate Search {hibernateSearchVersion} now:
 - requires using Hibernate ORM versions from the 6.2.x family.
 
 When migrating from previous versions of Hibernate Search
+
 - If you were using Hibernate ORM 6.2 and your corresponding Hibernate Search dependencies included references
 to artifacts ending with `-orm6` (e.g. `hibernate-search-mapper-orm-orm6`) just remove the `-orm6` suffix
 (e.g. use `hibernate-search-mapper-orm` instead) when you upgrade to this version of Hibernate Search.