elf: Remove bundled Guile source.

This module has been included in Guile as (system vm elf) since around version
2.1.

* guix/elf.scm: Delete file.
* CODEOWNERS: De-register module.
* Makefile.am (MODULES): Likewise.
* etc/teams.scm (core): Likewise.
* gnu/build/linux-modules.scm: Adjust imports.
* gnu/packages/gnuzilla.scm (icecat-minimal) [modules]: Likewise.
* gnu/packages/librewolf.scm (librewolf): Likewise.
* gnu/packages/sequoia.scm (sequoia): Likewise.
* gnu/packages/tor-browsers.scm (make-torbrowser): Likewise.
* gnu/packages/version-control.scm (hg-commitsigs): Likewise.
* guix/build/debug-link.scm: Likewise.
* guix/build/gnu-build-system.scm: Likewise.
* guix/build/gremlin.scm: Likewise.
* guix/build/meson-build-system.scm: Likewise.
* guix/grafts.scm (graft-derivation/shallow): Likewise.
* guix/scripts/pack.scm (wrapped-package): Likewise.
* tests/debug-link.scm: ("elf-debuglink", "set-debuglink-crc"): Likewise.
* tests/gremlin.scm: Likewise.
* guix/build-system/gnu.scm (%default-gnu-imported-modules): Remove (guix elf).

Change-Id: I86ac4237fdd820a6b54dc0fe7a7d10403a290ef9

etc/teams.scm

@@ -510,7 +510,6 @@ already exists.  Lookup team IDs among CURRENT-TEAMS."
               "guix/discovery.scm"
               "guix/docker.scm"
               "guix/download.scm"
-              "guix/elf.scm"
               "guix/ftp-client.scm"
               "guix/gexp.scm"
               "guix/git-authenticate.scm"