Remove delegation to non-scaled texture node on linear filter

gsk_gl_render_job_visit_texture_scale_node simply delegated its task to gsk_gl_render_job_visit_texture if the chosen filter is linear. This is not correct because gsk_gl_render_job_visit_texture uses either linear or trilinear filtering depending on the image scale.

Closes #5981 (closed)

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This is my first MR on any GNOME-related project, please tell me if there are formal errors or so.