core(ci): install certifi with conda, since pip cannot do it (#427)
core(ci): install certifi with conda, since pip cannot do it (#427)

* core(ci): install certifi with conda, since pip cannot do it
* force upgrade

maartenbreddels/vaex,maartenbreddels/vaex,maartenbreddels/vaex,maartenbreddels/vaex,maartenbreddels/vaex,maartenbreddels/vaex