gpg.ts contained ADOPTIUM_SIGNATURE_KEY_FINGERPRINT as an exported constant and used it as the default for keyFingerprint in verifyPackageSignature(), making the module look Adoptium-specific despite being a shared utility.

Changes:

• src/gpg.ts: Removed ADOPTIUM_SIGNATURE_KEY_FINGERPRINT constant; made keyFingerprint a required parameter in verifyPackageSignature() (no distro-specific default); removed Adoptium-specific comment
• src/distributions/temurin/installer.ts: Added export const ADOPTIUM_SIGNATURE_KEY_FINGERPRINT here, where it belongs; updated call site to use the local constant
• Tests: Updated gpg.test.ts to pass an explicit fingerprint; updated temurin-installer.test.ts to import the constant from the temurin installer instead of gpg

Check list:

• Mark if documentation changes are required.
• Mark if tests were added or updated to cover the changes.