buildspec: Bump buildspec to use OBS 31.0.4

[Trouffman]

Description

Bump the builspec.json to use OBS 31.0.4 - And solve the macOS build that fails.

Motivation and Context

Fix the macOS SDK detection error at #146 and preventing the success of #148 build.

Fixes #146.

How Has This Been Tested?

Tested on DistroAV project.

• Should pass the automated action here too.

Types of changes

Bug Fix in upstream that resolve bug in automated action & plugin builds.

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.

[glikely]

Also confirmed on obs-ptz plugin

[RytoEX]

Use the prefix "buildspec: " for the PR title and commit message subject.

[RytoEX]

Superseded by #151.