test_markdown: Fix type: ignore issues.
test_markdown: Fix type: ignore issues.

Signed-off-by: Anders Kaseorg <dfdb7392591db597bc41cf266a9c3bc12a2706e5@zulip.com>

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