The regex for removing the email address of the last translator from
PO-files contained two bugs causing it not to match:
- It didn't account for text after the email address and PO-files from Transifex contain the year of the last translation there.
- It expected a second \\n" at the end of the line, instead of \n".
This commit fixes both of these issues and simplifies the regexes. It
also ensures that the text after the email address is kept as well.