Fix buttons on header disappearing

I'm not sure if there's a better fix to this (it's kinda ugly)
but it at least prevents the buttons from disappearing.

The login button was disappearing when the title was big enough.

The correct fix would be to redesign the header to use a nav bar
that works on mobile e.g. using a hamburger icon and having a menu
that comes out. That's a bigger change.

Release-Notes: Fix buttons on header disappearing
Change-Id: I9da124be1ecd911cb16803fe709fb23a0860cd9e

polygerrit-ui/app/elements/core/gr-main-header/gr-main-header.ts

diff --git a/polygerrit-ui/app/elements/core/gr-main-header/gr-main-header.ts b/polygerrit-ui/app/elements/core/gr-main-header/gr-main-header.ts
index 34950b0..58c10f9 100644
--- a/polygerrit-ui/app/elements/core/gr-main-header/gr-main-header.ts
+++ b/polygerrit-ui/app/elements/core/gr-main-header/gr-main-header.ts
@@ -205,6 +205,7 @@
         nav {
           align-items: center;
           display: flex;
+          flex-wrap: wrap;
         }
         .bigTitle {
           color: var(--header-text-color);