Point Relx back to upstream

All PRs have been merged.

index/relx.mk

@@ -3,5 +3,5 @@ pkg_relx_name = relx
 pkg_relx_description = Sane, simple release creation for Erlang
 pkg_relx_homepage = https://github.com/erlware/relx
 pkg_relx_fetch = git
-pkg_relx_repo = https://github.com/essen/relx
+pkg_relx_repo = https://github.com/erlware/relx
 pkg_relx_commit = main