Fix format workflow failure by aligning d_multiply signature with Black

[Copilot]

The format GitHub Actions job failed because black --check --target-version=py314 adicts/ detected non-compliant formatting in adicts/functions.py. This change applies the minimal formatting-only update required for the job to pass.

• Root cause

  • adicts/functions.py contained a function signature layout that Black reformats under the repository’s CI configuration.

• Change applied

  • Reformatted d_multiply function definition to Black’s expected multiline style.
  • No behavioral or API changes.

def d_multiply(
    d: Mapping[A, Numeric], dmul: Mapping[A, Numeric]
) -> Mapping[A, Numeric]: