Fixed: Typo/unclear text in backup retention

Signed-off-by: Robin Dadswell <robin@dadswell.email>

frontend/src/Settings/General/BackupSettings.js

@@ -66,7 +66,7 @@ function BackupSettings(props) {
           type={inputTypes.NUMBER}
           name="backupRetention"
           unit="days"
-          helpText="Automatic backups older than the retention will be cleaned up automatically"
+          helpText="Automatic backups older than the retention period will be cleaned up automatically"
           onChange={onInputChange}
           {...backupRetention}
         />