Typos

We noticed several minor typos that do not affect code functionality, but nevertheless should be fixed.

• In TradingStorage, the parameter to setReferral is _refferal.

• In PairStorage, the gov-only function name is udpateSkewOpenFees.

• In ITradingStorage, updateType is an enum, so it should be capitalized.

• In VeTranche, in the unlock and forceUnlock functions, there is a duplicate delete lockStartTimeByTokenId[tokenId];.