Fix DH damage modifier calculation, and fix healing when current health > max

[Naton1]

This fixes two separate issues:

• One minor issue where the DH formula was slightly inaccurate, mostly noticeable if max hp was not 99, see https://oldschool.runescape.wiki/w/Dharok_the_Wretched%27s_equipment
• Issue when healing with current hp > max hp, for example, eat an anglerfish so HP is above 99, then cast blood barrage, HP will be reset to 99 currently