mypy: Fix annotations for json_encoder_for_html.
mypy: Fix annotations for json_encoder_for_html.

jackrzhang/zulip,eeshangarg/zulip,andersk/zulip,andersk/zulip,kou/zulip,hackerkid/zulip,kou/zulip,dhcrzf/zulip,andersk/zulip,mahim97/zulip,zulip/zulip,rht/zulip,showell/zulip,eeshangarg/zulip,mahim97/zulip,dhcrzf/zulip,shubhamdhama/zulip,eeshangarg/zulip,jackrzhang/zulip,shubhamdhama/zulip,rishig/zulip,mahim97/zulip,jackrzhang/zulip,rishig/zulip,dhcrzf/zulip,brainwane/zulip,zulip/zulip,punchagan/zulip,eeshangarg/zulip,rishig/zulip,andersk/zulip,brainwane/zulip,shubhamdhama/zulip,tommyip/zulip,hackerkid/zulip,rht/zulip,punchagan/zulip,hackerkid/zulip,hackerkid/zulip,punchagan/zulip,zulip/zulip,synicalsyntax/zulip,timabbott/zulip,hackerkid/zulip,zulip/zulip,brainwane/zulip,showell/zulip,brainwane/zulip,kou/zulip,timabbott/zulip,timabbott/zulip,rishig/zulip,zulip/zulip,jackrzhang/zulip,showell/zulip,showell/zulip,synicalsyntax/zulip,andersk/zulip,eeshangarg/zulip,synicalsyntax/zulip,rishig/zulip,dhcrzf/zulip,tommyip/zulip,timabbott/zulip,kou/zulip,dhcrzf/zulip,hackerkid/zulip,synicalsyntax/zulip,mahim97/zulip,brainwane/zulip,shubhamdhama/zulip,shubhamdhama/zulip,tommyip/zulip,dhcrzf/zulip,synicalsyntax/zulip,rht/zulip,rishig/zulip,showell/zulip,tommyip/zulip,eeshangarg/zulip,kou/zulip,andersk/zulip,tommyip/zulip,synicalsyntax/zulip,jackrzhang/zulip,shubhamdhama/zulip,rht/zulip,hackerkid/zulip,dhcrzf/zulip,andersk/zulip,rht/zulip,tommyip/zulip,tommyip/zulip,timabbott/zulip,rht/zulip,mahim97/zulip,synicalsyntax/zulip,kou/zulip,punchagan/zulip,timabbott/zulip,jackrzhang/zulip,brainwane/zulip,kou/zulip,zulip/zulip,eeshangarg/zulip,rht/zulip,punchagan/zulip,punchagan/zulip,zulip/zulip,mahim97/zulip,showell/zulip,jackrzhang/zulip,timabbott/zulip,showell/zulip,punchagan/zulip,shubhamdhama/zulip,rishig/zulip,brainwane/zulip