Enable GPG check in SLE repofile

Enable GPG check on SUSE SLE builds.

Tested locally

Before updating repofile

0462e329b96b:/ # zypper repos
Refreshing service 'container-suseconnect-zypp'.
Repository priorities are without effect. All enabled repositories share the same priority.

# | Alias   | Name    | Enabled | GPG Check | Refresh
--+---------+---------+---------+-----------+--------
1 | SLE_BCI | SLE_BCI | Yes     | ( p) Yes  | Yes

Update made

vi /etc/zypp/repos.d/SLE_BCI.repo

[SLE_BCI]
enabled=1
gpgcheck=1
autorefresh=1
baseurl=https://updates.suse.com/SUSE/Products/SLE-BCI/$releasever_major-SP$releasever_minor/$basearch/product/
priority=100

After update

0462e329b96b:/ # zypper repos
Refreshing service 'container-suseconnect-zypp'.
Repository priorities are without effect. All enabled repositories share the same priority.

# | Alias   | Name    | Enabled | GPG Check | Refresh
--+---------+---------+---------+-----------+--------
1 | SLE_BCI | SLE_BCI | Yes     | (r ) Yes  | Yes

#763 (moved)