Browser: remove waitForBugoutOnline

[Terkwood]

• We can remove the check for bugout to be online in gtp.js:

if (!this.gameId && this.entryMethod === EntryMethod.PLAY_BOT) {
          this.setupBotGame(this.botDifficulty);
        } else {
          // Until https://github.com/Terkwood/BUGOUT/issues/174
          // is completed, we need to wait for the system to
          // come online when we're playing against a human being.
          this.waitForBugoutOnline().then((a, b) => this.onBugoutOnline(a, b));
        }

• We should remove logic based on idleStatus in MultiplayerColorPrefModal.
• Make sure none of these changes break the gateway flow