Update database.rst

Rename session index `sessions_sess_time_idx` to `sessions_sess_lifetime_idx ` since index is added to `sess_lifetime` column

Author: ulinskas

session/database.rst

@@ -415,7 +415,7 @@ PostgreSQL
         sess_lifetime INTEGER NOT NULL,
         sess_time INTEGER NOT NULL
     );
-    CREATE INDEX sessions_sess_time_idx ON sessions (sess_lifetime);
+    CREATE INDEX sessions_sess_lifetime_idx ON sessions (sess_lifetime);
 
 Microsoft SQL Server
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