fix(typings): test our .d.ts with --noImplicitAny

This matches how DefinitelyTyped tests it, so we are
one step closer to publishing the same file we generate.

See #3195

docs/typescript-package/services/tsParser/getExportDocType.js

@@ -38,19 +38,17 @@ module.exports = function getExportDocType(log) {
       file: ts.getSourceFileOfNode(symbol.declarations[0]).fileName
     });
     return 'unknown';
-  }
+  };
 
   function getBlockScopedVariableDocType(symbol) {
 
     var node = symbol.valueDeclaration;
     while(node) {
       if ( node.flags & 0x2000 /* const */) {
-        // DefinitelyTyped is still TS 1.4 so const is not allowed.
-        // https://github.com/borisyankov/DefinitelyTyped/issues/4564
-        return 'var'; // change to const when targetting TS 1.5
+        return 'const';
       }
       node = node.parent;
     }
     return 'let';
   }
-};
+};