css: Decrease vertical space at top of feed.
css: Decrease vertical space at top of feed.

This is system unfortunately has a rather complicated calculation to
compute the offsets correctly, but the net effect here is that the top
section of the Zulip window is much more space-efficient.

Shrinking the tab bar underpadding, part of this change, fixes #4444.

We only need the underpadding to be as tall as the space above the
floating recipient bar, which is definitely less than 10px, so I don't
anticipate regressions caused by this.

mahim97/zulip,showell/zulip,timabbott/zulip,punchagan/zulip,timabbott/zulip,ryanbackman/zulip,punchagan/zulip,brainwane/zulip,verma-varsha/zulip,rishig/zulip,vaidap/zulip,rht/zulip,andersk/zulip,showell/zulip,jphilipsen05/zulip,zulip/zulip,brainwane/zulip,vaidap/zulip,timabbott/zulip,hackerkid/zulip,vabs22/zulip,timabbott/zulip,tommyip/zulip,mahim97/zulip,christi3k/zulip,brockwhittaker/zulip,rht/zulip,amanharitsh123/zulip,brainwane/zulip,Galexrt/zulip,eeshangarg/zulip,brockwhittaker/zulip,jackrzhang/zulip,brockwhittaker/zulip,shubhamdhama/zulip,amanharitsh123/zulip,showell/zulip,synicalsyntax/zulip,verma-varsha/zulip,showell/zulip,punchagan/zulip,zulip/zulip,synicalsyntax/zulip,mahim97/zulip,jrowan/zulip,dhcrzf/zulip,ryanbackman/zulip,brainwane/zulip,rishig/zulip,jrowan/zulip,jrowan/zulip,verma-varsha/zulip,dhcrzf/zulip,andersk/zulip,j831/zulip,zulip/zulip,rht/zulip,jackrzhang/zulip,zulip/zulip,showell/zulip,brainwane/zulip,rishig/zulip,shubhamdhama/zulip,zulip/zulip,Galexrt/zulip,dhcrzf/zulip,timabbott/zulip,punchagan/zulip,jackrzhang/zulip,jphilipsen05/zulip,eeshangarg/zulip,tommyip/zulip,j831/zulip,synicalsyntax/zulip,hackerkid/zulip,vaidap/zulip,vabs22/zulip,brockwhittaker/zulip,jackrzhang/zulip,jphilipsen05/zulip,jackrzhang/zulip,christi3k/zulip,andersk/zulip,jphilipsen05/zulip,christi3k/zulip,synicalsyntax/zulip,amanharitsh123/zulip,andersk/zulip,shubhamdhama/zulip,christi3k/zulip,dhcrzf/zulip,jackrzhang/zulip,dhcrzf/zulip,jphilipsen05/zulip,shubhamdhama/zulip,tommyip/zulip,ryanbackman/zulip,synicalsyntax/zulip,zulip/zulip,amanharitsh123/zulip,synicalsyntax/zulip,dhcrzf/zulip,dhcrzf/zulip,zulip/zulip,hackerkid/zulip,andersk/zulip,brockwhittaker/zulip,eeshangarg/zulip,kou/zulip,showell/zulip,mahim97/zulip,vaidap/zulip,hackerkid/zulip,kou/zulip,jackrzhang/zulip,rishig/zulip,amanharitsh123/zulip,Galexrt/zulip,j831/zulip,rht/zulip,shubhamdhama/zulip,timabbott/zulip,shubhamdhama/zulip,punchagan/zulip,tommyip/zulip,punchagan/zulip,eeshangarg/zulip,rht/zulip,ryanbackman/zulip,shubhamdhama/zulip,kou/zulip,rishig/zulip,vaidap/zulip,vabs22/zulip,eeshangarg/zulip,kou/zulip,kou/zulip,tommyip/zulip,j831/zulip,rishig/zulip,ryanbackman/zulip,brainwane/zulip,punchagan/zulip,kou/zulip,tommyip/zulip,vabs22/zulip,Galexrt/zulip,showell/zulip,hackerkid/zulip,Galexrt/zulip,Galexrt/zulip,rishig/zulip,ryanbackman/zulip,mahim97/zulip,j831/zulip,christi3k/zulip,brockwhittaker/zulip,amanharitsh123/zulip,verma-varsha/zulip,jrowan/zulip,jrowan/zulip,rht/zulip,vabs22/zulip,timabbott/zulip,synicalsyntax/zulip,jphilipsen05/zulip,kou/zulip,vabs22/zulip,hackerkid/zulip,j831/zulip,eeshangarg/zulip,jrowan/zulip,brainwane/zulip,christi3k/zulip,andersk/zulip,eeshangarg/zulip,verma-varsha/zulip,mahim97/zulip,tommyip/zulip,andersk/zulip,verma-varsha/zulip,vaidap/zulip,Galexrt/zulip,rht/zulip,hackerkid/zulip