Enable security warnings for command-line flags

Setting the policy to Enabled or leaving it unset means security warnings appear when potentially dangerous command-line flags are used to launch Chrome. Setting the policy to Disabled prevents security warnings from appearing when Chrome is launched with potentially dangerous command-line flags. On Microsoft® Windows®, this policy is only available on instances that are joined to a Microsoft® Active Directory® domain, joined to Microsoft® Azure® Active Directory® or enrolled in Chrome Enterprise Core. On macOS, this policy is only available on instances that are managed via MDM, joined to a domain via MCX or enrolled in Chrome Enterprise Core.