Fix Shield block chance calcs

[Blitz54]

Fixes#10097 partially

Description of the problem being solved:

Block chance on shields were scaling by increased on the item first, followed by base block chance. Instead it should add the base block chance to the shields armour block chance, and then scale by increased local mods.

Aegis Aurora should be
26 base +6 local base mod = 32
32 x 1.2 = 38.4

26 x 1.2 = 31.2
31.2 + 6 = 37.1

After screenshot: