Remove `FlowToken` Deposit and Withdraw events

[joshuahannan]

Issue To Be Solved

The FlowToken.TokensDeposited and FlowToken.TokensWithdrawn events take up unnecessary computation and space in transaction results now that the FungibleToken standard events exist. They should be removed

Suggest A Solution

• Work with all partners who rely on FlowToken events and tell them that they need to migrate their integrations to the FungibleToken events.
• Remove the event emissions and events from the contract
• Create an upgrade plan and post to the forum and discord well in advance
• Upgrade the contract on testnet and mainnet