BUG/MINOR: pollers: remove uneeded free in global init

BUG/MINOR: pollers: remove uneeded free in global init

Since commit d4604adeaa8c ("MAJOR: threads/fd: Make fd stuffs
thread-safe"), we init pollers per thread using a helper. It was still
correct for mono-thread mode until commit cd7879adc2c4 ("BUG/MEDIUM:
threads: Run the poll loop on the main thread too"). We now use a deinit
helper for all threads, making those free uneeded.

Only poll and select are affected by this very minor issue.

it could be backported from v1.8 to v2.1.

Fixes: cd7879adc2c4 ("BUG/MEDIUM: threads: Run the poll loop on the main
thread too")
Signed-off-by: William Dauchy <w.dauchy@criteo.com>