rtla/trace: Error message fixup

Use capital and change "tracer %s" to "%s tracer".

No functional change.

Link: https://lkml.kernel.org/r/361697d27431afefa64c67c323564205385c418d.1643990447.git.bristot@kernel.org

Fixes: b1696371

 ("rtla: Helper functions for rtla")
Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: linux-kernel@vger.kernel.org
Cc: linux-trace-devel@vger.kernel.org
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>