Fix: Small change to phi difference calculation in seed charge determination

[bschmookler]

Briefly, what does this PR introduce?

Essentially changes this line

if(dphi > M_PI) dphi = 2.*M_PI - dphi;

to
if(dphi > M_PI) dphi = dphi - 2.*M_PI;

This will affect a seed where, for example, the first hit is at phi = - 179.5 degrees and the second hit is at phi = + 179.5 degrees. In the prior version, dphi = 360 - 359 = +1 degrees, returning a positive charge. Now it will correctly return a negative charge.

This has a very small overall effect. For 10k single muons generated from (x,y,z) = (0,0,0) with eta [-4,4] and p = [0.5,20] GeV/c, we have 0.86% seed charge misidentification now, compared to 0.87% previously.

Thanks to @veprbl for pointing this out.

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?

No

Does this PR change default behavior?

Yes, change affects seed charge calculation for a small number of seeds

[github-actions]

Capybara summary for PR 1214

• rec_dis_10x100_minQ2=1000_craterlake
• rec_dis_10x100_minQ2=1_craterlake
• rec_dis_18x275_minQ2=1000_craterlake
• rec_dis_18x275_minQ2=1_craterlake
• rec_dis_5x41_minQ2=1_craterlake
• rec_e_1GeV_20GeV_craterlake
• rec_pi_1GeV_20GeV_craterlake

[osbornjd]

No suggestions, looks good