Fix CameraShakerInstance:UpdateShake's timestep

[kennethloeffler]

CameraShakerInstance:UpdateShake uses a variable timestep to perform the update, causing players with low FPS and players using FPS unlockers to experience very pronounced shaking. This PR changes CameraShakerInstance:UpdateShake to use a fixed timestep so that the effect is consistent regardless of FPS

Closes #4

[v-champion]

Can not attest to #4, but this updated code does not make the effect consistent regardless of FPS for me.

[salahh1]

Can not attest to #4, but this updated code does not make the effect consistent regardless of FPS for me.

try adding this from line 154 - 156, it worked for me

local dtscale = dt * 60
posAddShake = posAddShake + (shake * c.PositionInfluence * dtscale)
rotAddShake = rotAddShake + (shake * c.RotationInfluence * dtscale)