Restore [] where default arguments are not keywords

Reverts some changes of a36666c52115.

In the case of os's `mknod(filename[, mode=0600[, device=0]])`, I have nested
the [] as setting mode doesn't require to set device (but setting device
requires to set mode).
diff --git a/Doc/library/ossaudiodev.rst b/Doc/library/ossaudiodev.rst
index 515c701..08f118f 100644
--- a/Doc/library/ossaudiodev.rst
+++ b/Doc/library/ossaudiodev.rst
@@ -275,7 +275,7 @@
 simple calculations.
 
 
-.. method:: oss_audio_device.setparameters(format, nchannels, samplerate, strict=False)
+.. method:: oss_audio_device.setparameters(format, nchannels, samplerate[, strict=False])
 
    Set the key audio sampling parameters---sample format, number of channels, and
    sampling rate---in one method call.  *format*,  *nchannels*, and *samplerate*