generate-test-credentials: Fix shellcheck warnings.
generate-test-credentials: Fix shellcheck warnings.

In tools/setup/generate-test-credentials line 10:
password=$(./manage.py print_initial_password "$email" | fgrep "$email" | awk '{ print $2 }')
                                                         ^-- SC2197: fgrep is non-standard and deprecated. Use grep -F instead.

Signed-off-by: Anders Kaseorg <087231934ba8fcf78bc142ce37d193b895ac03c4@mit.edu>

brainwane/zulip,andersk/zulip,rht/zulip,shubhamdhama/zulip,jackrzhang/zulip,timabbott/zulip,zulip/zulip,punchagan/zulip,hackerkid/zulip,kou/zulip,dhcrzf/zulip,hackerkid/zulip,synicalsyntax/zulip,tommyip/zulip,showell/zulip,rht/zulip,shubhamdhama/zulip,showell/zulip,zulip/zulip,brainwane/zulip,eeshangarg/zulip,jackrzhang/zulip,timabbott/zulip,rishig/zulip,timabbott/zulip,hackerkid/zulip,rishig/zulip,andersk/zulip,showell/zulip,rht/zulip,kou/zulip,brainwane/zulip,shubhamdhama/zulip,synicalsyntax/zulip,dhcrzf/zulip,tommyip/zulip,zulip/zulip,tommyip/zulip,jackrzhang/zulip,eeshangarg/zulip,kou/zulip,punchagan/zulip,andersk/zulip,punchagan/zulip,dhcrzf/zulip,zulip/zulip,dhcrzf/zulip,eeshangarg/zulip,zulip/zulip,tommyip/zulip,rht/zulip,rishig/zulip,showell/zulip,hackerkid/zulip,andersk/zulip,kou/zulip,punchagan/zulip,showell/zulip,dhcrzf/zulip,timabbott/zulip,andersk/zulip,hackerkid/zulip,rishig/zulip,rishig/zulip,kou/zulip,synicalsyntax/zulip,zulip/zulip,brainwane/zulip,timabbott/zulip,punchagan/zulip,kou/zulip,hackerkid/zulip,showell/zulip,timabbott/zulip,rht/zulip,rishig/zulip,showell/zulip,eeshangarg/zulip,hackerkid/zulip,synicalsyntax/zulip,shubhamdhama/zulip,rht/zulip,punchagan/zulip,eeshangarg/zulip,kou/zulip,dhcrzf/zulip,brainwane/zulip,rishig/zulip,shubhamdhama/zulip,tommyip/zulip,jackrzhang/zulip,jackrzhang/zulip,andersk/zulip,eeshangarg/zulip,brainwane/zulip,brainwane/zulip,jackrzhang/zulip,zulip/zulip,synicalsyntax/zulip,synicalsyntax/zulip,eeshangarg/zulip,shubhamdhama/zulip,tommyip/zulip,jackrzhang/zulip,synicalsyntax/zulip,tommyip/zulip,andersk/zulip,rht/zulip,punchagan/zulip,timabbott/zulip,shubhamdhama/zulip,dhcrzf/zulip