test_decorators: Explain typo-looking expression.
test_decorators: Explain typo-looking expression.

The validate_api_key sentence may look a bit confusing since we are
using webhook_bot's email address but default_bot's API key.

At first sight, and without any context on these tests, it may look like
that's just a typo, but we do want it to be like it is right now because
that way the API key used doesn't correspond to the provided email
address (triggering some untested parts of our backend logic).

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