feat: remove EnterpriseEnrollmentViewProcessor pipeline step

[pwnage101]

The pipeline step was designed to replace platform logic which handled a code path that ONLY served Enterprise Coupon fulfillment. Coupons, however, were sunsetted in September 2025, so there was never any point in creating the pipeline step in the first place.

This commit de-registers and deletes the pipeline step.

ENT-12366

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.03%. Comparing base (78fc978) to head (b4e40cd).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2698      +/-   ##
==========================================
- Coverage   87.06%   87.03%   -0.03%     
==========================================
  Files         265      264       -1     
  Lines       17292    17251      -41     
  Branches     1708     1705       -3     
==========================================
- Hits        15055    15015      -40     
  Misses       1898     1898              
+ Partials      339      338       -1     

Flag	Coverage Δ
unittests	87.03% <ø> (-0.03%)	⬇️

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[brobro10000]

Clean removal — I confirmed there are no other references to EnterpriseEnrollmentViewProcessor or enterprise.filters.enrollment left anywhere else in the repo, so this is mergeable as-is. Left one small style nit inline, nothing blocking.

Two friendly reminders before merging:

• This also bumps enterprise/__init__.py to 8.15.0, same as #2696 and #2697, both open concurrently — whichever of the three lands last will need a version bump to avoid colliding with the others. Worth confirming merge order with those PRs' author (looks like the same person across all three).
• Please squash-merge into a single commit, and rebase against the latest master before merging in case a sibling PR lands first and touches CHANGELOG.rst/__init__.py underneath you.