Fix version of big.js

package.json

@@ -73,7 +73,7 @@
     "alphavantage": "2.2.0",
     "angular-material-css-vars": "2.1.0",
     "bent": "7.3.12",
-    "big.js": "^6.1.1",
+    "big.js": "6.1.1",
     "bootstrap": "4.6.0",
     "cache-manager": "3.4.3",
     "cache-manager-redis-store": "2.0.0",
@@ -124,7 +124,7 @@
     "@nrwl/node": "12.5.4",
     "@nrwl/tao": "12.5.4",
     "@nrwl/workspace": "12.5.4",
-    "@types/big.js": "^6.1.1",
+    "@types/big.js": "6.1.1",
     "@types/cache-manager": "3.4.0",
     "@types/jest": "26.0.20",
     "@types/lodash": "4.14.168",