GT-86: fix some typos

[ross-rosario]

Tacking those issues:

• "add 3rd party whitelist manager" should be: "add 3rd party whitelist managers"
• "and manage approval of token transfer between wallets" should be "and manage approval of token transfers between particularwallets."
• just noticed one more thing: please remove the space before the comma after "import and export your whitelist"