Typo in PR merged notification email footer (BB-7291)

There is a small typo in the footer of the email that is sent out when a PR has been merged.

#!text

This is an pull request notification from bitbucket.org.

You are receiving this either because you are the participating
in a pull request, or you are following it.

Two things

• This is an pull request -> This is a pull request
• ... because you are the participating in ... -> because you are participating in