"Your browser is managed by your organization" means that someone or some application has set a policy for your browser. It does not mean that there is an organization controlling your browser.
In a common example, an antivirus application has set one or more browser policies so the antivirus can check websites for malicious content.
'Policies' are a special type of configuration setting. Normally, users do not set browser policies. That's typically done by an organization's IT department, which is why Chromium-based browsers like Microsoft Edge and Google Chrome use the wording "Your browser is managed by your organization" to indicate that one or more browser policies have been set, even when no organization exists.
