fix(ci): override rpm sign command to use gpg backend

Fedora 43 defaults to rpm-sequoia for signing which ignores the
imported gpg key. Set %__gpg_sign_cmd explicitly to force gpg-based
signing with loopback pinentry. Remove diagnostics.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

rpm/rpmmacros

@@ -1 +1,2 @@
 %_gpg_name @GPG_NAME@
+%__gpg_sign_cmd %{__gpg} --batch --verbose --no-armor --pinentry-mode loopback --passphrase '' --no-secmem-warning -u "%{_gpg_name}" -sbo %{__signature_filename} -- %{__plaintext_filename}