Remove duplicate slash `/` in tracker URL inside to downloaded torrent file

[josecelano]

Relates to: torrust/torrust-index-gui#572.

As you can see in the sample the tracker URL contains a double / (http://tracker:7070//3PISvzYph3GYkjJvz39hhnUqANLeVC7r)

We should also add a test.

Sample torrent in JSON:

{
   "announce": "http://tracker:7070//3PISvzYph3GYkjJvz39hhnUqANLeVC7r",
   "announce-list": [
      [
         "http://tracker:7070//3PISvzYph3GYkjJvz39hhnUqANLeVC7r"
      ],
      [
         "udp://tracker.torrust-demo.com:6969"
      ],
      [
         "udp://tracker.coppersurfer.tk:6969/announce"
      ],
      [
         "udp://9.rarbg.com:2710/announce"
      ],
      [
         "udp://p4p.arenabg.com:1337"
      ],
      [
         "udp://tracker.leechers-paradise.org:6969"
      ],
      [
         "udp://tracker.internetwarriors.net:1337"
      ],
      [
         "udp://tracker.opentrackr.org:1337/announce"
      ],
      [
         "http://tracker.openbittorrent.com:80/announce"
      ],
      [
         "udp://opentracker.i2p.rocks:6969/announce"
      ],
      [
         "udp://tracker.internetwarriors.net:1337/announce"
      ],
      [
         "udp://tracker.leechers-paradise.org:6969/announce"
      ],
      [
         "udp://coppersurfer.tk:6969/announce"
      ],
      [
         "udp://tracker.zer0day.to:1337/announce"
      ]
   ],
   "creation date": 1713791389,
   "info": {
      "files": [
         {
            "length": 2142878501,
            "path": [
               "Spirited.Away.2001.1080p.BluRay.x264-[YTS.AM].mp4"
            ]
         },
         {
            "length": 58132,
            "path": [
               "www.YTS.AM.jpg"
            ]
         }
      ],
      "name": "Spirited Away (2001) [BluRay] [1080p] [YTS.AM]",
      "piece length": 524288,
      "pieces": "<hex>1D 99 72 BF 0A E7 F0 D8 61 86 D7 AE 3B 59 A9 EF FA 5E CB 04 2D DB 14 04 A3 C0 82 0E DA 0B 7F 73 E5 5B 07 84 31 45 0C 06 4C BF 59 22 89 87 82 6B 71 D9 A8 A4 3C EE 74 EF C3 6A 81 E4 1B 60 EF 8A 08 90 A9 03 54 98 3F 0E A2 59 85 4F F5 F4 26 97 B4 67 A6 1E D9 5F 77 88 DA 70 18  0D 9E E5 7D F6 7F 5C 5D 78 66 6F B1 F5 D9 B4 AA C9 17 FC 0C D3 20 4C 80 FB C7 EA</hex>"
   }
}

[josecelano]

I guess this problem was introduced in this PR.