[CLI]Minor code improvement in CLI, remove ts-ignore-next-line

[ashishb]

Description

Minor code improvement in CLI, remove ts-ignore-next-line.
Use new Web3().eth.accounts.privateKeyToAccount(privateKey).address

Tested

packages/cli] $ yarn run celocli account:new
yarn run v1.17.3
$ /Users/ashishb/celo/celo-monorepo5/node_modules/.bin/celocli account:new
TypeError: web3_1.default is not a constructor
    at Function.generateAccountAddressFromPrivateKey (~/celo/celo-monorepo5/packages/cli/src/commands/account/new.ts:33:12)
    at NewAccount.run (~/celo/celo-monorepo5/packages/cli/src/commands/account/new.ts:41:39)
    at NewAccount._run (~/celo/celo-monorepo5/node_modules/@oclif/command/lib/command.js:44:31)
    at <anonymous>
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

[codecov]

Codecov Report

Merging #796 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #796   +/-   ##
=======================================
  Coverage   67.05%   67.05%           
=======================================
  Files         241      241           
  Lines        7134     7134           
  Branches      475      475           
=======================================
  Hits         4784     4784           
  Misses       2273     2273           
  Partials       77       77

Flag	Coverage Δ
#mobile	67.05% <ø> (ø)	⬆️

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