Double autoflush for DAODs

I am wrapping up my QTs pub note on the side and @gemmeren pointed out that this 1 line MR would be a nice addition.

DAODs currently have an autoflush of 10MB and this is found to be a bit too small. Doubling the autoflush should make DAOD file sizes a couple % smaller (e.g. estimated 2% for TOPQ1) and reading a bit faster while not impacting the memory footprint during production too much. Maybe we can even consider 30MB, but I have no idea if DAOD production jobs are limited by memory. (probably not, since xAOD jobs require much more?) If you are curious about the details, have a look at pages 7 - 9 of https://cds.cern.ch/record/2654407/files/ATL-COM-SOFT-2019-001.pdf

I don't have exact numbers of how this would impact DAOD production, but since this is an easy change I figured it would be nice to just open the MR.

Adding the alsoTargeting:master label to sweep this into master as well.

Pinging potentially interested people: @jcatmore @elmsheus @akraszna