Add `-U` to pip install commands
Add `-U` to pip install commands

Follow up to https://github.com/freedomofpress/securedrop/pull/932#commitcomment-10353326

conorsch/securedrop,micahflee/securedrop,kelcecil/securedrop,jaseg/securedrop,micahflee/securedrop,micahflee/securedrop,conorsch/securedrop,heartsucker/securedrop,jrosco/securedrop,ageis/securedrop,garrettr/securedrop,garrettr/securedrop,heartsucker/securedrop,chadmiller/securedrop,jaseg/securedrop,chadmiller/securedrop,kelcecil/securedrop,jrosco/securedrop,jaseg/securedrop,heartsucker/securedrop,ehartsuyker/securedrop,kelcecil/securedrop,jrosco/securedrop,jrosco/securedrop,jaseg/securedrop,kelcecil/securedrop,GabeIsman/securedrop,chadmiller/securedrop,jaseg/securedrop,conorsch/securedrop,jrosco/securedrop,GabeIsman/securedrop,heartsucker/securedrop,ageis/securedrop,pwplus/securedrop,GabeIsman/securedrop,jeann2013/securedrop,GabeIsman/securedrop,GabeIsman/securedrop,jaseg/securedrop,conorsch/securedrop,ageis/securedrop,GabeIsman/securedrop,kelcecil/securedrop,garrettr/securedrop,chadmiller/securedrop,jeann2013/securedrop,jeann2013/securedrop,pwplus/securedrop,ageis/securedrop,ehartsuyker/securedrop,chadmiller/securedrop,ehartsuyker/securedrop,kelcecil/securedrop,jrosco/securedrop,pwplus/securedrop,conorsch/securedrop,garrettr/securedrop,ehartsuyker/securedrop,micahflee/securedrop,chadmiller/securedrop,ehartsuyker/securedrop,pwplus/securedrop,jeann2013/securedrop,pwplus/securedrop,pwplus/securedrop,jeann2013/securedrop,heartsucker/securedrop,jeann2013/securedrop,ehartsuyker/securedrop