Increase source count limit

[Deer-Spangle]

As mildly discussed in https://e621.net/forum_topics/34730

Currently there's a limit on source links for posts; there can be no more than 10 per post. There are 501 posts which hit this limit, and it seems rather restrictive? At a glance, 10 source links sounds like a lot! But given the recommendation to have 3 links per actual source (submission link, direct file link, and user gallery link), that's actually only really 3 actual sources that are allowed. Uploading an image to twitter, Furaffinity and Weasyl would take all your source links, and throw in deviantart, or furry network or something, and you run out.

I get that there must be a limit to prevent abuse, and I feel like moving it to 30 would be more than enough, without being an undue burden.

There are 501 posts hitting the cap of 10 sources But no posts come close to hitting the cap of 2048 character long sources. The closest is a google translate link in post 53245, which is 1655 characters long. (That source should probably be updated or removed.) After that one, the next ones are all around 1000 characters long, about half the limit. Obviously, more rows is more of a database burden than more columns, but it seems like sources are stored newline-delimited in one column anway. Rather than as a separate table. Given the source link length limit is so generous, it seems like the number of source links should also be a bit more generous than it is. Especially given the recommendations on source link usage carve that down to a third.