Move styles from dropdown-content to GrAutocompleteDropdown

Unclear why but adding the style to the host renders a scrollbar
when dropdown overflows but adding to dropdown-content does not
render the scrollbar.

Google-bug-id: b/258377097
Release-Notes: skip
Change-Id: I8849316d7dfa459dc6fdf5335b01c7ef486c696e
diff --git a/polygerrit-ui/app/elements/shared/gr-autocomplete-dropdown/gr-autocomplete-dropdown.ts b/polygerrit-ui/app/elements/shared/gr-autocomplete-dropdown/gr-autocomplete-dropdown.ts
index 3fd1b82..4005bb3 100644
--- a/polygerrit-ui/app/elements/shared/gr-autocomplete-dropdown/gr-autocomplete-dropdown.ts
+++ b/polygerrit-ui/app/elements/shared/gr-autocomplete-dropdown/gr-autocomplete-dropdown.ts
@@ -79,6 +79,11 @@
       css`
         :host {
           z-index: 100;
+          box-shadow: var(--elevation-level-2);
+          overflow: auto;
+          background: var(--dropdown-background-color);
+          border-radius: var(--border-radius);
+          max-height: 50vh;
         }
         :host([is-hidden]) {
           display: none;
@@ -105,13 +110,6 @@
         li.selected {
           background-color: var(--hover-background-color);
         }
-        .dropdown-content {
-          background: var(--dropdown-background-color);
-          box-shadow: var(--elevation-level-2);
-          border-radius: var(--border-radius);
-          max-height: 50vh;
-          overflow: auto;
-        }
         @media only screen and (max-height: 35em) {
           .dropdown-content {
             max-height: 80vh;