fix: remove unused AWS SDK v2 import

This was done to reduce init logs by removing the AWS SDK v2 deprecation
notice from the output.

src/backend/src/services/SNSService.js

@@ -20,8 +20,6 @@
 const { Endpoint } = require("../util/expressutil");
 const BaseService = require("./BaseService");
 
-const aws = require('aws-sdk');
-const sns = new aws.SNS();
 const { LRUCache: LRU } = require('lru-cache');
 const crypto = require('crypto');
 const axios = require('axios');
@@ -52,10 +50,6 @@ const TEST_CERT = ``;
 const TEST_MESSAGE = {};
 
 class SNSService extends BaseService {
-    static MODULES = {
-        AWS: require('aws-sdk'),
-    };
-
     _construct () {
         this.cert_cache = new LRU({
             // Guide uses 5000 here but that seems excessive
@@ -149,10 +143,6 @@ class SNSService extends BaseService {
         }).attach(app);
     }
 
-    _init () {
-        this.sns = new this.modules.AWS.SNS();
-    }
-
     async verify_message_ (message, options = {}) {
         let cert;
         if ( options.test_mode ) {