css: Use SCSS nesting for `.main-headline-text` in portico.scss.
css: Use SCSS nesting for `.main-headline-text` in portico.scss.

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