Increase default diskCache byte limit from 20 to 50MB(PINCache default)

[MussaCharles]

As discussed on our slack thread since PINCache have already been optimized we no longer need to trade default size limit, thus I have simply increased the default disk cache limit from the original 20 MB to 50MB to support larger objects in the cache.

NB: History to why the limit was set to 20MB can be found here

Thanks :)