deps: Remove @std/dotenv

Author: ThinaticSystem

deno.json

@@ -8,7 +8,6 @@
   "imports": {
     "@octokit/webhooks": "npm:@octokit/webhooks@^13.8.0",
     "@std/assert": "jsr:@std/assert@1",
-    "@std/dotenv": "jsr:@std/dotenv@^0.225.3",
     "@std/http": "jsr:@std/http@1",
     "misskey-js": "npm:misskey-js@^2025.4.1-alpha.2"
   },