Revert "Rename src/customization/xsl/pt_br.xml to pt-BR.xml"
This is not the right fix: this file should have the same
name as the original file from docbook-xsl.
If the fix had been easier, it would have been fixed already.
CCBUG: 400973
CCMAIL: yurchor@ukr.net
This reverts commit 54cc616215e5087ff77fb3905f98e010145c8fa9.