feat: rm JChainMultifactory

[wdconinc]

Briefly, what does this PR introduce?

This PR removes the JChainMultifactory, now that no factory is using it anymore.

TODO:

• [x] #1418
• [x] #1419

What kind of change does this PR introduce?

• [ ] Bug fix (issue #__)
• [x] 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?

No.

Does this PR change default behavior?

No.

[github-actions[bot]]

Capybara summary for PR 1421

• rec_dis_10x100_minQ2=0_craterlake
• rec_dis_10x100_minQ2=1000_craterlake
• rec_dis_18x275_minQ2=0_craterlake
• rec_dis_18x275_minQ2=1000_craterlake
• rec_dis_5x41_minQ2=0_craterlake
• rec_e_1GeV_20GeV_craterlake
• rec_pi_1GeV_20GeV_craterlake ^{_{Last updated 2024-05-07T12:34-04:00 005c00d04807a783eb326337d20c84a82aefbf2d}}

[wdconinc]

Old diffs. Wait for update.

[wdconinc]

@ruse-traveler Updated, check again.

[ruse-traveler]

@ruse-traveler Updated, check again.

Nice! Not seeing any diffs!