Spelling Errors

# Handle

hickuphh3


# Vulnerability details

### Impact

LongShort.sol 

- `re-uising` → `reusing`
- `visa versa` → `vice versa`
- `@param marketIndex An int32` → `@param marketIndex A uint32`
- `Non-existant` → `Non-existent`

Staker.sol

- `Explicitely` → `Explicitly`
- `extremeley` → `extremely`

YieldManagerAave.sol

- `revent` → `revert`

