If you have previously logged into Office 365 accounts for different business or school tenants, they may remain even when you sign out. This is how to remove old OneDrive accounts from File Explorer in Windows.
Windows + R and entering regedit.HKEY_CURRENT_USER > Software > Microsoft > OneDrive > Accounts > BusinessName.UserEmail value. Delete the entire folder containing that key.HKEY_CLASSES_ROOT > CLSID. Search (CTRL+F) for keyword: OneDrive.System.IsPinnedToNameSpaceTree value to 0.If the icon is still visible, restart your computer.