Bump search index version

`hasPassword` was added to events in the previous commits, so we need
to rebuild the index.

backend/src/search/mod.rs

@@ -42,7 +42,7 @@ pub(crate) use self::{
 
 /// The version of search index schema. Increase whenever there is a change that
 /// requires an index rebuild.
-const VERSION: u32 = 6;
+const VERSION: u32 = 7;
 
 
 // ===== Configuration ============================================================================