Allow feed to be actualized after being truncated (#2862)
Allow feed to be actualized after being truncated (#2862)

Before, on had to wait for the cache to expire before being able to
refresh a feed that had been truncated via the Web interface.
Now, one can "delete all articles" and hit "actualize" imediately after
without problem.
Useful for testing filters, debugging e.g.
https://github.com/FreshRSS/FreshRSS/issues/2806
marienfressinaud/FreshRSS,FreshRSS/FreshRSS,aledeg/FreshRSS,Alkarex/FreshRSS,romibi/FreshRSS,aledeg/FreshRSS,Alkarex/FreshRSS,marienfressinaud/FreshRSS,marienfressinaud/FreshRSS,aledeg/FreshRSS,romibi/FreshRSS,Alkarex/FreshRSS,FreshRSS/FreshRSS,Alkarex/FreshRSS,FreshRSS/FreshRSS,romibi/FreshRSS,marienfressinaud/FreshRSS,romibi/FreshRSS,aledeg/FreshRSS,FreshRSS/FreshRSS