kernel: sched: default TIMESLICE_SIZE to 20

Sets the default for CONFIG_TIMESLICE_SIZE to 20 to approximate the
historical clamping behavior that was removed in 405611d.

Signed-off-by: Daniel Mangum <georgedanielmangum@gmail.com>

Author: hasheddan

kernel/Kconfig

@@ -653,7 +653,7 @@ config TIMESLICING
 
 config TIMESLICE_SIZE
 	int "Time slice size (in ms)"
-	default 0
+	default 20
 	range 0 $(INT32_MAX)
 	depends on TIMESLICING
 	help