[PWGEM] add option for at least one photon in Dalitz Skimmer

[lgansbartl]

No description provided.

[github-actions]

O2 linter results: ❌ 0 errors, ⚠️ 43 warnings, 🔕 11 disabled

[alibuild]

Error while checking build/O2Physics/staging for 70f6d79 at 2026-09-21 17:10:

No log files found

Full log here.

[alibuild]

Error while checking build/O2Physics/code-check for 70f6d79 at 2026-09-21 18:47:

## sw/BUILD/O2Physics-code-check-latest/log
--
========== List of issues found ==========
++ echo 'Found 11 errors and 0 warnings.'
Found 11 errors and 0 warnings.
++ [[ 11 -gt 0 ]]
++ cat /sw/BUILD/881bb5c49875f0df97b3180c9816fb506f6a7546/O2Physics-code-check/errors.txt
PWGEM/PhotonMeson/TableProducer/skimmerPrimaryElectronFromDalitzEE.h:39:1: error: included header AnalysisTask.h is not used directly [misc-include-cleaner,-warnings-as-errors]
PWGEM/PhotonMeson/TableProducer/skimmerPrimaryElectronFromDalitzEE.h:70:1: error: using declarations in the global namespace in headers are prohibited [google-global-names-in-headers,-warnings-as-errors]
PWGEM/PhotonMeson/TableProducer/skimmerPrimaryElectronFromDalitzEE.h:71:1: error: using declarations in the global namespace in headers are prohibited [google-global-names-in-headers,-warnings-as-errors]
PWGEM/PhotonMeson/TableProducer/skimmerPrimaryElectronFromDalitzEE.h:72:1: error: using declarations in the global namespace in headers are prohibited [google-global-names-in-headers,-warnings-as-errors]
PWGEM/PhotonMeson/TableProducer/skimmerPrimaryElectronFromDalitzEE.h:73:1: error: using declarations in the global namespace in headers are prohibited [google-global-names-in-headers,-warnings-as-errors]
PWGEM/PhotonMeson/TableProducer/skimmerPrimaryElectronFromDalitzEE.h:74:1: error: using declarations in the global namespace in headers are prohibited [google-global-names-in-headers,-warnings-as-errors]
PWGEM/PhotonMeson/TableProducer/skimmerPrimaryElectronFromDalitzEE.h:75:1: error: using declarations in the global namespace in headers are prohibited [google-global-names-in-headers,-warnings-as-errors]
PWGEM/PhotonMeson/TableProducer/skimmerPrimaryElectronFromDalitzEE.h:76:1: error: using declarations in the global namespace in headers are prohibited [google-global-names-in-headers,-warnings-as-errors]
PWGEM/PhotonMeson/TableProducer/skimmerPrimaryElectronFromDalitzEE.h:77:1: error: using declarations in the global namespace in headers are prohibited [google-global-names-in-headers,-warnings-as-errors]
PWGEM/PhotonMeson/TableProducer/skimmerPrimaryElectronFromDalitzEE.h:78:1: error: using declarations in the global namespace in headers are prohibited [google-global-names-in-headers,-warnings-as-errors]
PWGEM/PhotonMeson/TableProducer/skimmerPrimaryElectronFromDalitzEE.h:79:1: error: using declarations in the global namespace in headers are prohibited [google-global-names-in-headers,-warnings-as-errors]
++ [[ 0 -gt 0 ]]
++ [[ 11 -gt 0 ]]
++ exit 1
--

Full log here.

[jokonig]

code-checker errors are not introduced by this PR. They have to be fixed in another PR.