Sign-in flow fails for personal MS accounts with email addresses with capital characters in them

[msalaman]

Original issue brought up by customer in this bug opened for Github Copilot for Azure: microsoft/GitHub-Copilot-for-Azure#175

User tries to signs in to their Microsoft account to use the @Azure extension with an email address that has capital characters they are unable to login due to the following error:
Selecting either option doesn't work and just causes same error to appear

Issue is because of an equality check here:

vscode/src/vs/workbench/api/browser/mainThreadAuthentication.ts

Line 274 in c9dd842

&& accountToCreate.label !== session.account.label