Fix license metadata, link rot, and Rubocop warnings

[mlinksva]

A handful of small fixes and cleanups:

• zlib: Remove subtle extra space in license text (warranty. In → warranty. In)
• BSD-4-Clause: Replace Choco-solver example (moved to BSD-3-Clause per 📢 License Change: Moving to BSD-3-Clause chocoteam/choco-solver#1169) with Sileo
• OSL-3.0: Point explanation link to Wayback Machine snapshot since rosenlaw.com appears to have expired
• script/check-approval: Replace monkey-patched TrueClass#to_s / FalseClass#to_s with a yes_no helper (Rubocop)
• spec/spec_helper.rb: Use Array#to_h instead of each_with_object (Rubocop)

Based on work from #1333.

[Copilot]

Pull request overview

This PR makes small cleanup fixes across license metadata files and Ruby tooling to reduce lint warnings and address link rot in license notes, improving the reliability and consistency of the repository’s license data and scripts.

Changes:

• Update several license metadata entries (zlib whitespace, BSD-4-Clause “using” example, OSL-3.0 note link).
• Refactor script/check-approval to remove global TrueClass/FalseClass monkey-patching in favor of a yes_no helper.
• Simplify SPDX list hashing in spec/spec_helper.rb using Array#to_h.

Show a summary per file

File	Description
spec/spec_helper.rb	Simplifies SPDX license list conversion to a hash (to_h) to satisfy Rubocop/style.
script/check-approval	Replaces boolean to_s monkey-patches with a yes_no formatter for table output.
_licenses/zlib.txt	Fixes an extra whitespace in the zlib license text.
_licenses/osl-3.0.txt	Replaces a dead link with a Wayback Machine snapshot link.
_licenses/bsd-4-clause.txt	Updates the “using” example list to reflect upstream license relocation.

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• Files reviewed: 4/5 changed files
• Comments generated: 1