update-prod-static: Reduce verbosity of logging.
update-prod-static: Reduce verbosity of logging.

Previously, update-prod-static would produce thousands of lines of
basically useless output in `var/log/update-prod-static.log`.

synicalsyntax/zulip,kou/zulip,kou/zulip,synicalsyntax/zulip,synicalsyntax/zulip,kou/zulip,zulip/zulip,punchagan/zulip,punchagan/zulip,rht/zulip,zulip/zulip,timabbott/zulip,hackerkid/zulip,andersk/zulip,synicalsyntax/zulip,shubhamdhama/zulip,hackerkid/zulip,timabbott/zulip,eeshangarg/zulip,andersk/zulip,eeshangarg/zulip,shubhamdhama/zulip,zulip/zulip,showell/zulip,eeshangarg/zulip,zulip/zulip,showell/zulip,timabbott/zulip,showell/zulip,punchagan/zulip,eeshangarg/zulip,hackerkid/zulip,andersk/zulip,showell/zulip,brainwane/zulip,synicalsyntax/zulip,eeshangarg/zulip,timabbott/zulip,zulip/zulip,rht/zulip,andersk/zulip,timabbott/zulip,punchagan/zulip,showell/zulip,shubhamdhama/zulip,synicalsyntax/zulip,shubhamdhama/zulip,rht/zulip,timabbott/zulip,andersk/zulip,brainwane/zulip,zulip/zulip,showell/zulip,kou/zulip,andersk/zulip,shubhamdhama/zulip,showell/zulip,brainwane/zulip,shubhamdhama/zulip,hackerkid/zulip,brainwane/zulip,hackerkid/zulip,punchagan/zulip,eeshangarg/zulip,hackerkid/zulip,kou/zulip,punchagan/zulip,zulip/zulip,shubhamdhama/zulip,brainwane/zulip,hackerkid/zulip,brainwane/zulip,kou/zulip,rht/zulip,rht/zulip,andersk/zulip,kou/zulip,synicalsyntax/zulip,rht/zulip,brainwane/zulip,punchagan/zulip,eeshangarg/zulip,timabbott/zulip,rht/zulip