[extractor/niconico] Always use HTTPS for requests

This prevents MITM attacks from malicious parties like insane ISPs

Closes #5469

yt_dlp/extractor/niconico.py

@@ -231,7 +231,7 @@ def _get_heartbeat_info(self, info_dict):
             or self._parse_json(
                 self._html_search_regex(
                     'data-api-data="([^"]+)"',
-                    self._download_webpage('http://www.nicovideo.jp/watch/' + video_id, video_id),
+                    self._download_webpage('https://www.nicovideo.jp/watch/' + video_id, video_id),
                     'API data', default='{}'),
                 video_id))
 
@@ -390,7 +390,7 @@ def _real_extract(self, url):
 
         try:
             webpage, handle = self._download_webpage_handle(
-                'http://www.nicovideo.jp/watch/' + video_id, video_id)
+                'https://www.nicovideo.jp/watch/' + video_id, video_id)
             if video_id.startswith('so'):
                 video_id = self._match_id(handle.geturl())
 
@@ -728,7 +728,7 @@ def _entries(self, url, item_id, query=None, note='Downloading page %(page)s'):
             webpage = self._download_webpage(url, item_id, query=query, note=note % {'page': page_num})
             results = re.findall(r'(?<=data-video-id=)["\']?(?P<videoid>.*?)(?=["\'])', webpage)
             for item in results:
-                yield self.url_result(f'http://www.nicovideo.jp/watch/{item}', 'Niconico', item)
+                yield self.url_result(f'https://www.nicovideo.jp/watch/{item}', 'Niconico', item)
             if not results:
                 break