perf: Remove unused pointer task_ctx

The pointer task_ctx is being assigned a value that is not read, the
assignment is redundant and so is the pointer. Remove it

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20221028122545.528999-1-colin.i.king@gmail.com