remove atob and btoa dependencies from bower.json (#3017)

fix #3010

Author: HackbrettXXX

bower.json

@@ -13,10 +13,7 @@
   ],
   "moduleType": ["amd", "globals", "node", "es6"],
   "keywords": ["pdf"],
-  "dependencies": {
-    "atob": "^2.1.2",
-    "btoa": "^1.2.1"
-  },
+  "dependencies": {},
   "optionalDependencies": {
     "canvg": "^3.0.6",
     "core-js": "^3.6.0",