/login/: Remove previous alerts before displaying new alerts.
/login/: Remove previous alerts before displaying new alerts.

The issue is that the server wants to display an error when you make a
request and fail, but the jQuery form validator also wants to display
errors at the same time. This removes the server errors to display the
jQuery.

Fixes: #8239.

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