Maintainer merge checklist

• Title is descriptive/clear for inclusion in release notes.
• Applied a Component: xxx label.
• Applied the api-deprecation or api-break label.
• Applied the release-highlight label to be highlighted in release notes.
• Added to the milestone version it was merged into.
• Unittests are included in PR.
• Properly documented, including versionadded, versionchanged as needed.

mock gl backend should be treated as angle, as sdl should not manage the egl context.

Previously did not failed as sdl have been built with OpenGL support, but since the introduction of the ANGLE EGL provider sdl is being built without OpenGL support enabled.

During wheel tests, performed with KIVY_GL_BACKEND=mock, the pipeline is failing as sdl is trying to create a window with OpenGL support, even if we opted out.