Only count upcoming events in tab title

[fbacall]

Summary of changes

• Show upcoming count instead of all event count (with asterisk if no upcoming but some past events).

Motivation and context

Past events are not as relevant to users.

Screenshots

Checklist

• I have read and followed the CONTRIBUTING guide.
• I confirm that I have the authority necessary to make this contribution on behalf of its copyright owner and agree
  to license it to the TeSS codebase under the
  BSD license.