PyDoc: replace references to the deprecated "bgl" with "gpu"

Also correct bullet-points in gpu.state.blend_set.

doc/python_api/examples/blf.py

@@ -3,7 +3,7 @@ Hello World Text Example
 ++++++++++++++++++++++++
 
 Example of using the blf module. For this module to work we
-need to use the OpenGL wrapper :class:`~bgl` as well.
+need to use the GPU module :mod:`gpu` as well.
 """
 # import stand alone modules
 import blf

scripts/modules/gpu_extras/presets.py

@@ -8,7 +8,8 @@ def draw_circle_2d(position, color, radius, *, segments=None):
 
     :arg position: 2D position where the circle will be drawn.
     :type position: Sequence[float]
-    :arg color: Color of the circle (RGBA). To use transparency GL_BLEND has to be enabled.
+    :arg color: Color of the circle (RGBA).
+       To use transparency blend must be set to ``ALPHA``, see: :func:`gpu.state.blend_set`.
     :type color: Sequence[float]
     :arg radius: Radius of the circle.
     :type radius: float

source/blender/python/gpu/gpu_py_state.cc

@@ -77,6 +77,7 @@ PyDoc_STRVAR(
     "   Defines the fixed pipeline blending equation.\n"
     "\n"
     "   :arg mode: The type of blend mode.\n"
+    "\n"
     "      * ``NONE`` No blending.\n"
     "      * ``ALPHA`` The original color channels are interpolated according to the alpha "
     "value.\n"