parameters: remove unneeded usleep

According to @bkueng this was to schedule other processes but can now be
removed.

src/lib/parameters/parameters.cpp

@@ -1280,8 +1280,6 @@ param_import_internal(int fd, bool mark_saved)
 
 	do {
 		result = bson_decoder_next(&decoder);
-		// FIXME: it's unclear why this usleep is needed in the first place
-		//px4_usleep(1);
 
 	} while (result > 0);