refactor(fetcher): remove dead selfSignedCert code

Drop the unused self-signed certificate branch that disabled TLS
verification via rejectUnauthorized: false.

The option was not wired from configuration, so behavior is unchanged
while removing a high-severity CodeQL finding:
https://github.com/MagicMirrorModules/MMM-CalendarExt2/security/code-scanning/1

Author: KristjanESPERANTO

lib/calendar-fetcher.js

@@ -1,4 +1,3 @@
-const https = require("node:https");
 const Log = require("logger");
 
 /**
@@ -75,9 +74,6 @@ class CalendarFetcher {
     }
 
     const headers = {"User-Agent": this.options.userAgent};
-    const agent = this.options.selfSignedCert
-      ? new https.Agent({rejectUnauthorized: false})
-      : null;
 
     if (this.auth) {
       if (this.auth.method === "bearer") {
@@ -90,8 +86,7 @@ class CalendarFetcher {
     let delay = this.reloadInterval;
     try {
       const response = await fetch(this.url, {
-        headers,
-        agent
+        headers
       });
       if (response.ok) {
         this.suspendUntil = null;