Adapt to virtual sensor changes in w3c/sensors#475

w3c/sensors#475 removed the "virtual sensor type" item from the "virtual
sensor metadata" struct and turned it into a string that is referenced from
the automation bits as well as (optionally) defined by a sensor type.

Adapt to it here by removing mentions of `[=virtual sensor metadata/virtual
sensor type=]` from the spec and adding virtual sensor types to each sensor
type defined here.

Fixes w3c#58.

index.bs

@@ -139,6 +139,8 @@ The <dfn id="gyroscope-sensor-type">Gyroscope</dfn> <a>sensor type</a> has the f
  :: Invoke the [=generic sensor permission revocation algorithm=] with "<code><a permission>gyroscope</a></code>".
  : [=Default sensor=]
  :: The device's main gyroscope sensor.
+ : [=Virtual sensor type=]
+ :: "<code><dfn data-lt="gyroscope virtual sensor type">gyroscope</dfn></code>"
 
 A [=latest reading=] of a {{Sensor}} of <a>Gyroscope</a> <a>sensor type</a> includes three [=map/entries=]
 whose [=map/keys=] are "x", "y", "z" and whose [=map/values=] contain current <a>angular
@@ -244,9 +246,9 @@ This section extends [[GENERIC-SENSOR#automation]] by providing [=Gyroscope=]-sp
 
 The [=per-type virtual sensor metadata=] [=map=] must have the following [=map/entry=]:
 : [=map/key=]
-:: "`gyroscope`"
+:: "<code>[=gyroscope virtual sensor type|gyroscope=]</code>"
 : [=map/value=]
-:: A [=virtual sensor metadata=] whose [=virtual sensor metadata/virtual sensor type=] is [=Gyroscope=] and [=reading parsing algorithm=] is [=parse xyz reading=].
+:: A [=virtual sensor metadata=] whose [=virtual sensor metadata/reading parsing algorithm=] is [=parse xyz reading=].
 
 Acknowledgements {#acknowledgements}
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