doc: remove redundant 'Example:' and similar notes

Some nits were also fixed in passing.

PR-URL: https://github.com/nodejs/node/pull/22537
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/https.md

@@ -76,8 +76,6 @@ added: v0.3.4
  [`tls.createSecureContext()`][] and [`http.createServer()`][].
 * `requestListener` {Function} A listener to be added to the `'request'` event.
 
-Example:
-
 ```js
 // curl -k https://localhost:8000/
 const https = require('https');
@@ -134,8 +132,6 @@ Like [`http.get()`][] but for HTTPS.
 string, it is automatically parsed with [`new URL()`][]. If it is a [`URL`][]
 object, it will be automatically converted to an ordinary `options` object.
 
-Example:
-
 ```js
 const https = require('https');
 
@@ -193,8 +189,6 @@ The following additional `options` from [`tls.connect()`][] are also accepted:
 string, it is automatically parsed with [`new URL()`][]. If it is a [`URL`][]
 object, it will be automatically converted to an ordinary `options` object.
 
-Example:
-
 ```js
 const https = require('https');
 
@@ -239,8 +233,6 @@ const req = https.request(options, (res) => {
 
 Alternatively, opt out of connection pooling by not using an [`Agent`][].
 
-Example:
-
 ```js
 const options = {
   hostname: 'encrypted.google.com',