Added a description to the picth_scale property in the AudioStreamPlayer classes.

doc/classes/AudioStreamPlayer.xml

@@ -57,6 +57,7 @@
 			If the audio configuration has more than two speakers, this sets the target channels. See [code]MIX_TARGET_*[/code] constants.
 		</member>
 		<member name="pitch_scale" type="float" setter="set_pitch_scale" getter="get_pitch_scale">
+			Changes the pitch and the tempo of the audio.
 		</member>
 		<member name="playing" type="bool" setter="_set_playing" getter="is_playing">
 			If [code]true[/code] audio is playing.

doc/classes/AudioStreamPlayer2D.xml

@@ -63,6 +63,7 @@
 			Maximum distance from which audio is still hearable.
 		</member>
 		<member name="pitch_scale" type="float" setter="set_pitch_scale" getter="get_pitch_scale">
+			Changes the pitch and the tempo of the audio.
 		</member>
 		<member name="playing" type="bool" setter="_set_playing" getter="is_playing">
 			If [code]true[/code] audio is playing.

doc/classes/AudioStreamPlayer3D.xml

@@ -87,6 +87,7 @@
 			Decides if audio should pause when source is outside of 'max_distance' range.
 		</member>
 		<member name="pitch_scale" type="float" setter="set_pitch_scale" getter="get_pitch_scale">
+			Changes the pitch and the tempo of the audio.
 		</member>
 		<member name="playing" type="bool" setter="_set_playing" getter="is_playing">
 			If [code]true[/code], audio is playing.