Wrong repository size on overview page after using 'hg convert' (BB-4797)

Hi. I'm Paul. Was cleaning up our repo on Bitbucket from old files and .dlls.

I've done 'hg convert' and reduced size of our repository from 45 MB to 1.5 MB and pushed new repo to Bitbucket, updating existing one (hg push --force). After that, I went to 'Admin' - 'Strip changesets', and deleted old repository completely.

Now, if I close our updated repo, I will really download only those 1.5 MB from Bitbucket - no joke. But on the repo overview page there is still that old huge number, even bigger - 47.5 MB.

I think it will scare people wrongfully O_0

Go to our repo (https://bitbucket.org/alex_razv/selfrenderedcontrol) to reproduce the issue.

Also, I attached a couple of screenshots: size of repo in Bitbucket UI and actual size of downloaded '.hg' folder.