Pin signing-clients to version 1.4.1
Pin signing-clients to version 1.4.1

This is required in preparation for
https://github.com/mozilla/signing-clients/pull/22 to not getting pulled
into AMO without proper testing after merging.

Fixes #7094

eviljeff/olympia,diox/olympia,eviljeff/olympia,kumar303/olympia,atiqueahmedziad/addons-server,aviarypl/mozilla-l10n-addons-server,mozilla/addons-server,mozilla/olympia,harry-7/addons-server,bqbn/addons-server,psiinon/addons-server,kumar303/olympia,wagnerand/addons-server,wagnerand/olympia,diox/olympia,kumar303/addons-server,wagnerand/addons-server,wagnerand/addons-server,tsl143/addons-server,wagnerand/olympia,mozilla/olympia,bqbn/addons-server,wagnerand/addons-server,lavish205/olympia,tsl143/addons-server,bqbn/addons-server,atiqueahmedziad/addons-server,diox/olympia,wagnerand/olympia,kumar303/addons-server,harry-7/addons-server,atiqueahmedziad/addons-server,kumar303/addons-server,eviljeff/olympia,mozilla/addons-server,lavish205/olympia,lavish205/olympia,mozilla/addons-server,kumar303/olympia,lavish205/olympia,eviljeff/olympia,diox/olympia,tsl143/addons-server,kumar303/olympia,bqbn/addons-server,aviarypl/mozilla-l10n-addons-server,mozilla/olympia,psiinon/addons-server,atiqueahmedziad/addons-server,kumar303/addons-server,tsl143/addons-server,wagnerand/olympia,mozilla/olympia,psiinon/addons-server,psiinon/addons-server,harry-7/addons-server,aviarypl/mozilla-l10n-addons-server,aviarypl/mozilla-l10n-addons-server,harry-7/addons-server,mozilla/addons-server