Drop the unreachable _files check in the ready interval

_onMessage calls _stopReady() before assigning _files, so the interval
was always cleared before _files could become truthy; the guard inside
the interval was dead code. The interval now just times out or
re-announces.

Author: bdraco

web.esphome.io/src/dashboard/ew-web-flash.ts

@@ -98,10 +98,6 @@ class EWWebFlash extends LitElement {
     let waited = 0;
     this._readyTimer = window.setInterval(() => {
       waited += 500;
-      if (this._files) {
-        this._stopReady();
-        return;
-      }
       if (waited >= 10000) {
         // Opener crashed, navigated away, or speaks a mismatched protocol; give
         // the user a terminal state instead of an endless spinner.