Fix duplicated line breaks in subtitles converted to srt

[Paco8]

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• [x] My changes respect the Kodi add-on development rules
• [x] My code is both Python 2 and 3 compatible
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Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
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Description:

I'm using HBO Spain, I found a problem with a subtitle, this one: https://production-static.hboespana.com/p/3b1f95c-00b2c24d769/5d8cbcca77d341e580d62f3faa42a30c.xml

This subtitle contains \n characters but the conversion function to srt also converts "<br />" to \n, so the resulting srt contains duplicated \n characters, which creates empty lines between the texts:

1
00:00:50,240 --> 00:00:55,560
Le he dicho: "Señora,

los asientos no han encogido...

2
00:00:55,720 --> 00:00:58,600
...es su trasero el que ha crecido".

3
00:01:41,040 --> 00:01:44,640
Lo siento, señor. Esta cabina

es solo para primera clase.

When this happens kodi only displays the first line of the text.

I think the problem can be fixed just by removing the "\n" characters from the original text.

[arvvoid]

Hello, tnx