Increase budget

I forgot that we budgeted a bit more in
fundraising.git:budget/2019.mdwn and that we have a separate budget for
outreach material.

wiki/src/jobs/illustrations_how_tails_work.mdwn

@@ -139,7 +139,7 @@ SVG standard.
 
 ### Budget
 
-Billable hours paid up to 2 000€, including meetings.
+Billable hours paid up to 2 500€, including meetings.
 
 Design considerations
 =====================