search pills: Fix pills misalignment bugs visible in firefox.
search pills: Fix pills misalignment bugs visible in firefox.

The `.search_icon` lies inside the `.pill_container` so we had to
remove it's display attribute which should have no visual changes.

We add `flex-wrap: nowrap` to prevent the cursor from moving onto
a new line, below the pills.

Fixes #15480.

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