GL Renderer: fix memory leak in GraphicsContext


OpenGL helpers weren't getting deleted.

Pick-to: 6.12 6.11 6.8
Change-Id: Icbe35aa7411baab3c079bf7888947114103f6c8a
Reviewed-by: Mike Krus <mike.krus@kdab.com>
commit7a91ee0f2885b363c09267001529c86b511ae703
parentd1c6f03b5b84a3e6b238a3ba5c3209ea43a89223
authorMauro Persano <mauro.persano@kdab.com>
committerMauro Persano <mauro.persano@kdab.com>
commit timeTue, 8 Sep 2026 10:51:05 +0000