remove: remove constants/float16/lanczos-gamma-g

The value added in #9022 is not appropriate for half-precision
numerical approximation. As observed for the equivalent `float64`
and `float32` constants, the value we use for `g` depends on what
approximation we use in our gamma function implementations. In
general, we should only add this constant if and when we add a
half-precision gamma approximation. Something we are not likely
to do anytime soon.

BREAKING CHANGE: remove `constants/float16/lanczos-gamma-g`

This feature was only recently added and has not been published.
As such, the impact of removing this constant should be negligible
for downstream users.

Ref: #9022

---
type: pre_commit_static_analysis_report
description: Results of running static analysis checks when committing changes.
report:
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Author: kgryte