PyAPI: remove deprecated 2D_/3D_ prefix for built-in shader names

Names passed to gpu.shader.from_builtin()
no longer skip the 2D_/3D_ prefix.

doc/python_api/examples/gpu.1.py

@@ -129,7 +129,7 @@ import gpu
 from gpu_extras.batch import batch_for_shader
 
 coords = [(1, 1, 1), (-2, 0, 0), (-2, -1, 3), (0, 1, 1)]
-shader = gpu.shader.from_builtin('3D_UNIFORM_COLOR')
+shader = gpu.shader.from_builtin('UNIFORM_COLOR')
 batch = batch_for_shader(shader, 'LINES', {"pos": coords})