tracing: remove legacy select of MARKERS by context switch tracing

The context switch tracer was made before tracepoints were mature, and
the original version used markers. This is no longer true and this
patch removes the select.

Reported-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/Kconfig

@@ -60,7 +60,6 @@ config EVENT_TRACING
 	bool
 
 config CONTEXT_SWITCH_TRACER
-	select MARKERS
 	bool
 
 # All tracer options should select GENERIC_TRACER. For those options that are