Add policy for deleting CPC repo content (#1358)

Closes #1346.

---------

Signed-off-by: Tobie Langel <tobie@unlockopen.com>
Co-authored-by: Chris De Almeida <ctcpip@users.noreply.github.com>

Author: tobie

governance/GOVERNANCE.md

@@ -168,6 +168,12 @@ The pull request may be fast-tracked if two CPC members approve the fast-trackin
 
 CPC members may request fast-tracking of pull requests they did not author. In that case only, the request itself is also one fast-track approval. Upvote the comment anyway to avoid any doubt.
 
+### Removing obsolete content
+
+The CPC aims to keep this repository up-to-date and devoid of obsolete information. The default is therefore to remove obsolete information. It is always possible to open a pull request to restore deleted information. Please explain the rationale for doing so in that case, and ensure such information is clearly labeled as obsolete.
+
+To facilitate locating deleted information, please pay close attention to commit messages when deleting content. In particular, note what content is being removed and why.
+
 [cpc repo]: https://github.com/openjs-foundation/cross-project-council
 [CPC charter section 5]: ../CPC-CHARTER.md#section-5-responsibilities-and-expectations-of-the-cpc
 [cpc charter decision making]: ../CPC-CHARTER.md#section-9-decision-making