css: Use SCSS nesting in portico-signin.scss for `.alert`.
css: Use SCSS nesting in portico-signin.scss for `.alert`.

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