Increase Rebase Reward to 250 USDx

With high network congestion, calling rebase is too expensive.

A simple fix will be to increase the rebase reward to 250 USDx.

Even with neutral rebases every day for 1 year, this only results in an inflation of 182500, USDx (250 x 2 x 365).

This can be temporary patch until we get something more dynamic (variable gas fee based reward)