Allow for shiftKey modifier in search hotkey

Search keyboard shortcut '/' requires the key combo (shift+7) on a
German keyboard layout. This change whitelists the shiftKey modifier in
the forward slash keypress handler.

Bug: Issue 7672
Change-Id: Iacc0adda03158f61fa7f653d7d29db3e40c3da79

polygerrit-ui/app/elements/core/gr-search-bar/gr-search-bar.js

@@ -335,8 +335,9 @@
     },
 
     _handleForwardSlashKey(e) {
+      const keyboardEvent = this.getKeyboardEvent(e);
       if (this.shouldSuppressKeyboardShortcut(e) ||
-          this.modifierPressed(e)) { return; }
+          (this.modifierPressed(e) && !keyboardEvent.shiftKey)) { return; }
 
       e.preventDefault();
       this.$.searchInput.focus();