Update locales-pt-BR.xml

[isabellypsilva]

I made some changes following the ABNT standard.

• There is generally no differentiation for the plural of abbreviations. Example: The abbreviations for organizer and organizers are org. (There is no difference);
• The abbreviation for volume is v. and not vol.
• The best translation for paper conference is “trabalho de evento”.

CSL Locales Pull Request Template

You're about to create a pull request to the CSL locales repository.
If you haven't done so already, see http://docs.citationstyles.org/en/stable/translating-locale-files.html for instructions on how to translate CSL locale files, and https://github.com/citation-style-language/styles/blob/master/CONTRIBUTING.md on how to submit your changes.
In addition, please fill out the pull request template below.

Description

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Checklist

• Check that you're listed as a <translator> in the <info> block at the beginning of the file.

[isabellypsilva]

I'm giving up on this pull request because I saw that there is another one open.