[frontend] Add 'repo_gpgcheck=0' to .repo file template

Zypper automatically rejects repositories that don't have
signed repository metadata by default, so this flag is
set to indicate that the copr repository metadata isn't
signed like the packages in the repository are, and
Zypper should use the repository anyway.

frontend/coprs_frontend/coprs/templates/coprs/copr.repo

@@ -5,5 +5,6 @@ type=rpm-md
 skip_if_unavailable=True
 gpgcheck={{ config.REPO_GPGCHECK | default("1")}}
 gpgkey={{ pubkey_url | fix_url_https_backend  }}
+repo_gpgcheck=0
 enabled=1
 enabled_metadata=1