Clarity edit (home-assistant#12271)

Somebody pointed out today that the docs make it sound like HA _always_ is responsible for the location update requests, and I can see how that's been taken that way. Adding a little clarity (hopefully).

source/_integrations/device_tracker.markdown

@@ -34,7 +34,7 @@ The following optional parameters can be used with any platform:
 
 | Parameter           | Default | Description                                                                                                                                                                                                                                                                                                                                                                               |
 |----------------------|---------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
-| `interval_seconds`   | 12      | Seconds between each scan for new devices                                                                                                                                                                                                                                                                                                                                                 |
+| `interval_seconds`   | 12      | Seconds between each scan for new devices. This only applies to local device trackers, not applications that push updates. |
 | `consider_home`      | 180     | Seconds to wait till marking someone as not home after not being seen. This parameter is most useful for households with Apple iOS devices that go into sleep mode while still at home to conserve battery life. iPhones will occasionally drop off the network and then re-appear. `consider_home` helps prevent false alarms in presence detection when using IP scanners such as Nmap. `consider_home` accepts various time representations, (e.g., the following all represents 3 minutes: `180`, `0:03`, `0:03:00`)  |
 
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