dev-lang/rust: remove 'changelog-seen'

it has been removed rust-lang/rust#123711

Signed-off-by: Mathieu Tortuyaux <mtortuyaux@microsoft.com>

Author: tormath1

sdk_container/src/third_party/coreos-overlay/dev-lang/rust/rust-1.79.0.ebuild

@@ -357,7 +357,6 @@ src_configure() {
 
 	local cm_btype="$(usex debug DEBUG RELEASE)"
 	cat <<- _EOF_ > "${S}"/config.toml
-		changelog-seen = 2
 		[llvm]
 		download-ci-llvm = false
 		optimize = $(toml_usex !debug)