added info on microphone sample format

(cherry picked from commit eb5a42d0bc28809f954861291c20d2ed6bed6d0f)

doc/classes/AudioEffectCapture.xml

@@ -5,7 +5,7 @@
 	</brief_description>
 	<description>
 		AudioEffectCapture is an AudioEffect which copies all audio frames from the attached audio effect bus into its internal ring buffer.
-		Application code should consume these audio frames from this ring buffer using [method get_buffer] and process it as needed, for example to capture data from a microphone, implement application defined effects, or to transmit audio over the network.
+		Application code should consume these audio frames from this ring buffer using [method get_buffer] and process it as needed, for example to capture data from a microphone, implement application defined effects, or to transmit audio over the network. When capturing audio data from a microphone, the format of the samples will be stereo 32-bit floating point PCM.
 	</description>
 	<tutorials>
 	</tutorials>