Update README.md with LiquidityRemoved emit fixed and other small ch…

[GeemoCandama]

• Switched tokenAmount and ethWithdrawn in LiquidityRemoved emit to reflect the implemented LiquidityRemoved event.

  event LiquidityRemoved(
      address liquidityRemover,
      uint256 liquidityWithdrawn,
      uint256 tokensOutput,
      uint256 ethOutput
  );

• Updated the Chackpoint 5: Liquidity by changing the statement that previously said k will be unchanged. As Checkpoint 3 says "The k only changes as liquidity is added."
• other small tiny grammar fixes

[rin-st]

Thank you @GeemoCandama, lgtm!