Relax anti-DOS protection for the SVN service

[strk]

It looks like 30 requests within a single second are easy to make when it comes to fetching SVN code. See ​postgis:#3553

This ticket is to raise the DOSSiteCount limit a little bit, after checking that it is really legit to hit that hard, even if it is for an SVN checkout.

[strk]

It was found to be DOSPageCount (3) to be the cause of blocking, not DOSSiteCount (which is 50, btw, not 30): ​postgis:#3553#comment:6

[wildintellect]

It's reasonable to set the svn limits rather high, since a spammer won't have commit rights without a project admin manually adding them to the correct project group. So more than a few hundred hits a minute for all of the possible options.

[strk]

It doesn't take commit access to successfully run a denial-of-service attack