Fix: Accept additional correct solutions in L14.P2 damage check

[madison-nicole]

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• The commit message follows our guidelines.
• For bug fixes and features:
  • You tested the changes.

Related issue (if applicable): #1388

What kind of change does this PR introduce?

Bug fix: widens the static check for practice L14.P2 "Reducing damage at
higher levels" so it accepts more correct solutions.

Does this PR introduce a breaking change?

No. All previously accepted solutions still pass; the change only adds
alternatives to the existing GDExpr.any_of pattern in
TestReducingDamage.gd. No practice text or error messages were touched,
so there is no translation churn.

New feature or change

What is the current behavior?

The check "Multiplication Is Used To Reduce Damage Amount" only matches
amount *= 0.5 and amount = amount * 0.5 (operand order is already
flexible, so amount = 0.5 * amount also passes). Other solutions that
produce exactly the specified behavior, half damage above level 2, full
damage below, fail with "It looks like amount isn't reduced by a
percentage," even though the behavioral check passes.

What is the new behavior?

Two additional forms are accepted, both of which keep the practice's
intent of assigning the reduced value back to the parameter:

• amount -= amount * 0.5
• amount /= 2 (also matches 2.0, since literal matching uses Variant ==)

Out of scope, up to the maintainer

• Reducing at the subtraction site (health -= amount * 0.5 with an
  else branch which is the exact code from L14.P2 Reducing damage at higher levels: check rejects correct solutions that don't reassign amount #1388): accepting it would drop the
  assign-to-parameter requirement entirely, which is a lesson-design call
  for a practice about multiplication.
• amount = amount / 2: easy to add with GDExpr.bin_op(..., OP_DIVISION)
  if wanted.