[Subtitles] fix smi subtitles to use quoted start tags

[howie-f]

Description

kodi would not pick up subtitles if tags are quoted in smi-file.

Motivation and Context

closes #17418

How Has This Been Tested?

i've tested this change with both smi-files provided by the reporting user
<SYNC Start=1398403><P Class=KOKRCC></P></SYNC> ... was working before
<SYNC Start="1398403"><P Class="KOKRCC"></P></SYNC> ... now also working

Types of change

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code follows the Code Guidelines of this project
• I have read the Contributing document

[phunkyfish]

The the bug report the working example was:
<SYNC Start=1398403><P Class=KOKRCC></P></SYNC>

and not:

<SYNC Start=1398403><P Class="KOKRCC"></P></SYNC>

Your change handles the quotes for the start attribute. How about the class attribute? Or is that not required?

[howie-f]

c+p error. handling the class is not required. i tested with the delivered files in the zip
EDIT: c+p error corrected ;)

[phunkyfish]

Nice

[howie-f]

i checked this pr once again with a smi-sample from wikipedia containing:

notice the manually "quoted classes" and "start attribute"

<!-- Open play menu, choose Captions and Subtiles, On if available -->
<!-- Open tools menu, Security, Show local captions when present -->

<SYNC Start="0">
  <P Class="ENUSCC" ID=Source>The Speaker</P>
  <P Class="ENUSCC">SAMI 0000 text</P>

  <P Class="FRFRCC" ID=Source>Le narrateur</P>
  <P Class="FRFRCC">Texte SAMI 0000</P>
</SYNC>

resulting screenshot (english):

resulting screenshot (french):

so i think we're good to go with this. best we can do atm.

[phunkyfish]

Will merge shortly if you want to create the backport PR?

[phunkyfish]

@howie-f also, would you like to join our slack, in case you have any queries which are not PR ready?

If interested PM your email address on the kodi forum.

[howie-f]

@phunkyfish thanks, that was quick.
seems like i cannot pm on the forum, but you can find the valid email in my commits