UndoAfterBurner: skip particles that are not created by generator

[veprbl]

Briefly, what does this PR introduce?

This provides a file size reduction:

before 3.1M
after 2.7M

What kind of change does this PR introduce?

• Bug fix (issue #__)
• New feature (issue #__)
• Documentation update
• Other: __

Please check if this PR fulfills the following:

• Tests for the changes have been added
• Documentation has been added / updated
• Changes have been communicated to collaborators

Does this PR introduce breaking changes? What changes might users need to make to their code?

Unlikely.

Does this PR change default behavior?

Yes

[github-actions]

Capybara summary for PR 1683

• rec_dis_10x100_minQ2=0_craterlake
• rec_dis_10x100_minQ2=1000_craterlake_tracking_only
• rec_dis_18x275_minQ2=0_craterlake_18x275
• rec_dis_18x275_minQ2=1000_craterlake_18x275
• rec_dis_5x41_minQ2=0_craterlake_5x41
• rec_e_1GeV_20GeV_craterlake
• rec_pi_1GeV_20GeV_craterlake
  ^{_{Last updated 2024-12-01T19:01-05:00 e032c34}}

[ajentsch]

This is very nice, refined functionality! Thank you!