Remove unnecessary tsconfig.json flags. (#2067)

tsconfig.base.json enables "strict" now which implicitly enables "strictFunctionTypes", "strictNullChecks", and "noImplicitAny" so we don't need to do so explicitly.

Disabling "alwaysStrict" was unnecessary since we have no violations.

Author: Michael Lehenbauer

packages/firestore/tsconfig.json

@@ -2,10 +2,6 @@
   "extends": "../../config/tsconfig.base.json",
   "compilerOptions": {
     "outDir": "dist",
-    "strictFunctionTypes": true,
-    "strictNullChecks": true,
-    "noImplicitAny": true,
-    "alwaysStrict": false,
     "noImplicitThis": false,
     "strictBindCallApply": false,
     "strictPropertyInitialization": false