docs: remove [email protected]

I no longer have access to the mailing list. See
#5007.

Pull-Request: #5020.

README.md

@@ -16,9 +16,8 @@ This repository is the central place for Rust development of the [libp2p](https:
   many protocols in this repository.
 
 - For **security related issues** please [file a private security vulnerability
-  report](https://github.com/libp2p/rust-libp2p/security/advisories/new)
-  or reach out to [[email protected]](mailto:[email protected]). Please do not
-  file a public issue on GitHub.
+  report](https://github.com/libp2p/rust-libp2p/security/advisories/new) . Please do not file a
+  public issue on GitHub.
 
 - To **report bugs, suggest improvements or request new features** please open a
   GitHub issue on this repository.

SECURITY.md

@@ -7,5 +7,3 @@ By default we provide security patches for the latest released version only. On
 ## Reporting a Vulnerability
 
 Please do not file a public issue on GitHub. Instead, please [file a private security vulnerability report](https://github.com/libp2p/rust-libp2p/security/advisories/new).
-
-If you need further assistance, please reach out to [[email protected]](mailto:[email protected]).