Fix duplicate-label warnings

[rkratky]

Description

Fixes the following build warnings:

docs/SRU/reference/exception-MariaDB-Galera-Updates.rst:33: WARNING: duplicate label upstream_release_policy, other instance in docs/SRU/reference/exception-Intel-Graphics-Updates.rst
docs/SRU/reference/exception-MariaDB-Galera-Updates.rst:49: WARNING: duplicate label ubuntu_releases_affected, other instance in docs/SRU/reference/exception-Intel-Graphics-Updates.rst
docs/SRU/reference/exception-MariaDB-Galera-Updates.rst:86: WARNING: duplicate label quality_assurance, other instance in docs/SRU/reference/exception-Intel-Graphics-Updates.rst
docs/SRU/reference/exception-MariaDB-Galera-Updates.rst:148: WARNING: duplicate label security_uploads, other instance in docs/SRU/reference/exception-Intel-Graphics-Updates.rst
docs/SRU/reference/exception-MariaDB-Galera-Updates.rst:172: WARNING: duplicate label process, other instance in docs/SRU/reference/exception-Intel-Graphics-Updates.rst
docs/SRU/reference/exception-MariaDB-Galera-Updates.rst:195: WARNING: duplicate label sru_template, other instance in docs/SRU/reference/exception-Intel-Graphics-Updates.rst
docs/SRU/reference/exception-MariaDB-Galera-Updates.rst:33: WARNING: duplicate label upstream_release_policy, other instance in docs/SRU/reference/exception-Intel-Graphics-Updates.rst
docs/SRU/reference/exception-MariaDB-Galera-Updates.rst:49: WARNING: duplicate label ubuntu_releases_affected, other instance in docs/SRU/reference/exception-Intel-Graphics-Updates.rst
docs/SRU/reference/exception-MariaDB-Galera-Updates.rst:86: WARNING: duplicate label quality_assurance, other instance in docs/SRU/reference/exception-Intel-Graphics-Updates.rst
docs/SRU/reference/exception-MariaDB-Galera-Updates.rst:148: WARNING: duplicate label security_uploads, other instance in docs/SRU/reference/exception-Intel-Graphics-Updates.rst
docs/SRU/reference/exception-MariaDB-Galera-Updates.rst:172: WARNING: duplicate label process, other instance in docs/SRU/reference/exception-Intel-Graphics-Updates.rst
docs/SRU/reference/exception-MariaDB-Galera-Updates.rst:195: WARNING: duplicate label sru_template, other instance in docs/SRU/reference/exception-Intel-Graphics-Updates.rst

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Checklist

• I have read and followed the Ubuntu Project contributing guide
• [n/a] My pull request is linked to an existing issue (if applicable)
• I have tested my changes, and they work as expected

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Additional notes (optional)

This wen unnoticed/ignored for quite a long time. We might want to consider re-enabling "fail on warning". WDYT, @s-makin?

[panlinux]

+1, thanks