Remove auxiliary input source and tracker example

Author: klausw

index.bs

@@ -1544,9 +1544,7 @@ Similarly, the Valve Index controller is backwards compatible with the HTC Vive
 
 Note: {{XRInputSource}}s in an {{XRSession}}'s {{XRSession/inputSources}} array are "live". As such values within them are updated in-place. This means that it doesn't work to save a reference to an {{XRInputSource}}'s attribute on one frame and compare it to the same attribute in a subsequent frame to test for state changes, because they will be the same object. Therefore developers that wish to compare input state from frame to frame should copy the content of the state in question.
 
-An [=XR input source=] is a <dfn>primary input source</dfn> if it supports a <dfn>primary action</dfn>. The [=primary action=] is a platform-specific action that, when engaged, produces {{XRSession/selectstart}}, {{XRSession/selectend}}, and {{XRSession/select}} events. Examples of possible [=primary action=]s are pressing a trigger, touchpad, or button, speaking a command, or making a hand gesture. If the platform guidelines define a recommended primary input then it should be used as the [=primary action=], otherwise the user agent is free to select one. The device MUST support at least one [=primary input source=].
-
-An [=XR input source=] is a <dfn>auxiliary input source</dfn> if it does not support a [=primary action=]. Examples include motion trackers without buttons, or secondary screen touches on a multitouch device.
+Each [=XR input source=] MUST define a <dfn>primary action</dfn>. The [=primary action=] is a platform-specific action that, when engaged, produces {{XRSession/selectstart}}, {{XRSession/selectend}}, and {{XRSession/select}} events. Examples of possible [=primary action=]s are pressing a trigger, touchpad, or button, speaking a command, or making a hand gesture. If the platform guidelines define a recommended primary input then it should be used as the [=primary action=], otherwise the user agent is free to select one.
 
 <div class="algorithm" data-algorithm="on-input-start">