chore: fix invalid use of typeof operator (#3076)

Author: nbbeeken

.eslintrc.json

@@ -20,6 +20,7 @@
     "prettier/prettier": "error",
     "tsdoc/syntax": "warn",
     "no-console": "error",
+    "valid-typeof": "error",
     "eqeqeq": [
       "error",
       "always",

src/cmap/stream_description.ts

@@ -55,16 +55,16 @@ export class StreamDescription {
 
   receiveResponse(response: Document): void {
     this.type = parseServerType(response);
-    RESPONSE_FIELDS.forEach(field => {
-      if (typeof response[field] != null) {
+    for (const field of RESPONSE_FIELDS) {
+      if (response[field] != null) {
         this[field] = response[field];
       }
 
       // testing case
       if ('__nodejs_mock_server__' in response) {
         this.__nodejs_mock_server__ = response['__nodejs_mock_server__'];
       }
-    });
+    }
 
     if (response.compression) {
       this.compressor = this.compressors.filter(c => response.compression?.includes(c))[0];