Mercy's chain beam heals

[voignamir-2764]

@Yara-11173

Make chain beams vastly weaker, main beam stronger, reduce the duration and we may have a decent, more skillful ultimate in our hands.

for the duration to be smaller i think the main beam should be 90 HPS with 40 HPS chain beams, idk a 75/35ish would be weak with a shorter duration