From another answer, this double slash dot is common
RedirectMatch 404 /\\.svn(/|$)
Since we're matching "/.svn" etc., why isn't this a single slash to escape the period?
Double escaping is allowed here but not really required. So both of these rules will work:
RedirectMatch 410 /\\.svn(/|$)
OR
RedirectMatch 410 /\.svn(/|$)