chore: Update CODEOWNERS to remove ownership from most (#28941)

## **Description**

The CODEOWNERS file has been updated to remove ownership from most
files, to give us more time to plan which files the platform should own,
and to give teams more time to consolidate their features.

Also, ownership of the CODEOWNERS file itself was moved to the extension
security team (it was accidentally set to privacy reviewers).

[![Open in GitHub
Codespaces](https://github.com/codespaces/badge.svg)](https://codespaces.new/MetaMask/metamask-extension/pull/28941?quickstart=1)

## **Related issues**

This is an adjustment to recent changes made in #28851

## **Manual testing steps**

N/A

## **Screenshots/Recordings**

N/A

## **Pre-merge author checklist**

- [x] I've followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask
Extension Coding
Standards](https://github.com/MetaMask/metamask-extension/blob/main/.github/guidelines/CODING_GUIDELINES.md).
- [x] I've completed the PR template to the best of my ability
- [x] I’ve included tests if applicable
- [x] I’ve documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
- [x] I’ve applied the right labels on the PR (see [labeling
guidelines](https://github.com/MetaMask/metamask-extension/blob/main/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

## **Pre-merge reviewer checklist**

- [ ] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [ ] I confirm that this PR addresses all acceptance criteria described
in the ticket it closes and includes the necessary testing evidence such
as recordings and or screenshots.

.github/CODEOWNERS

@@ -1,4 +1,6 @@
 # Lines starting with '#' are comments.
+
+# GUIDELINES:
 # Each line is a file pattern followed by one or more owners.
 # Owners bear a responsibility to the organization and the users of this
 # application. Repository administrators have the ability to merge pull
@@ -7,9 +9,11 @@
 # follows all policies or without full understanding of the impact of
 # those changes on build, release and publishing outcomes.
 
-*                                    @MetaMask/extension-platform
-development/                         @MetaMask/extension-platform
-lavamoat/                            @MetaMask/extension-platform @MetaMask/supply-chain
+# LavaMoat policy changes can highlight security risks. Teams are encouraged to
+# audit these changes on their own, and leave their analysis in a comment.
+# These codeowners will review this analysis, and review the policy changes in
+# further detail if warranted.
+lavamoat/                            @MetaMask/extension-devs @MetaMask/supply-chain
 
 # The offscreen.ts script file that is included in the offscreen document html
 # file is responsible, at present, for loading the snaps execution environment
@@ -45,7 +49,7 @@ privacy-snapshot.json                @MetaMask/extension-privacy-reviewers
 # of contributors. Modifications to this file result in a modification of
 # that agreement and can only be approved by those with the knowledge
 # and responsibility to publish libraries under the MetaMask name.
-.github/CODEOWNERS                   @MetaMask/extension-privacy-reviewers
+.github/CODEOWNERS                   @MetaMask/extension-security-team
 
 # For now, restricting approvals inside the .devcontainer folder to devs
 # who were involved with the Codespaces project.