feat(pg): rework constructor documentation. Closes #41167 (#41174)

- remove outdated comment
- add link to the documentation
- update test with parameterless ctor

Thanks!

types/pg/index.d.ts

@@ -144,10 +144,15 @@ export class Connection extends events.EventEmitter {
     end(): void;
 }
 
+/**
+ * {@link https://node-postgres.com/api/pool}
+ */
 export class Pool extends events.EventEmitter {
-    // `new Pool('pg://user@localhost/mydb')` is not allowed.
-    // But it passes type check because of issue:
-    // https://github.com/Microsoft/TypeScript/issues/7485
+    /**
+     * Every field of the config object is entirely optional.
+     * The config passed to the pool is also passed to every client
+     * instance within the pool when the pool creates that client.
+     */
     constructor(config?: PoolConfig);
 
     readonly totalCount: number;

types/pg/pg-tests.ts

@@ -124,6 +124,12 @@ client.end()
   .then(() => console.log('client has disconnected'))
   .catch(err => console.error('error during disconnection', err.stack));
 
+// pg.Pool
+// https://node-postgres.com/api/pool
+
+// no params ctor
+const poolParameterlessCtor = new Pool();
+
 const poolOne = new Pool({
   connectionString: 'postgresql://dbuser:secretpassword@database.server.com:3211/mydb'
 });