tracing: Remove unused variable 'dups'

Reported by Clang [-Wunused-but-set-variable]

'commit c193707d

 ("tracing: Remove code which merges duplicates")'
This commit removed the code which merges duplicates in detect_dups(),
but forgot to delete the variable 'dups' which used to merge
duplicates in the loop.

Now only 'total_dups' is needed, remove 'dups' for clean code.

Link: https://lkml.kernel.org/r/20220930103236.253985-1-chenzhongjin@huawei.com

Signed-off-by: Chen Zhongjin <chenzhongjin@huawei.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>