[PaswordSafe] change of release branch to 'release/4.x'

[David Heidelberg <david ixit cz>]

Hello guys,

thank you for great work on PasswordSafe translations and I'd like to 
announce, that we're switching 4.x branch development into 
'release/4.x' branch.

Development iwill continue in the master branch and also there is high 
possibility we'll rename it to main branch soon. If that happends, I'll 
let you know.
Have a nice day
David Heidelberg