Cleanup: prefer 'arg' over 'params' for sphinx documentation

While both are supported, 'arg' is in more common use so prefer it.

source/blender/python/mathutils/mathutils_Color.c

@@ -1102,7 +1102,7 @@ PyDoc_STRVAR(
     "   the OpenColorIO configuration. The notable exception is user interface theming colors, "
     "   which are in sRGB color space.\n"
     "\n"
-    "   :param rgb: (r, g, b) color values\n"
+    "   :arg rgb: (r, g, b) color values\n"
     "   :type rgb: 3d vector\n");
 PyTypeObject color_Type = {
     PyVarObject_HEAD_INIT(NULL, 0) "Color", /* tp_name */

source/blender/python/mathutils/mathutils_Euler.c

@@ -774,9 +774,9 @@ PyDoc_STRVAR(
     "\n"
     "   .. seealso:: `Euler angles <https://en.wikipedia.org/wiki/Euler_angles>`__ on Wikipedia.\n"
     "\n"
-    "   :param angles: Three angles, in radians.\n"
+    "   :arg angles: Three angles, in radians.\n"
     "   :type angles: 3d vector\n"
-    "   :param order: Optional order of the angles, a permutation of ``XYZ``.\n"
+    "   :arg order: Optional order of the angles, a permutation of ``XYZ``.\n"
     "   :type order: str\n");
 PyTypeObject euler_Type = {
     PyVarObject_HEAD_INIT(NULL, 0) "Euler", /* tp_name */

source/blender/python/mathutils/mathutils_Matrix.c

@@ -3321,8 +3321,7 @@ PyDoc_STRVAR(
     "   This object gives access to Matrices in Blender, supporting square and rectangular\n"
     "   matrices from 2x2 up to 4x4.\n"
     "\n"
-    "   :param rows: Sequence of rows.\n"
-    "      When omitted, a 4x4 identity matrix is constructed.\n"
+    "   :arg rows: Sequence of rows. When omitted, a 4x4 identity matrix is constructed.\n"
     "   :type rows: 2d number sequence\n");
 PyTypeObject matrix_Type = {
     PyVarObject_HEAD_INIT(NULL, 0) "Matrix", /*tp_name*/

source/blender/python/mathutils/mathutils_Quaternion.c

@@ -1662,9 +1662,9 @@ PyDoc_STRVAR(quaternion_doc,
              "\n"
              "   This object gives access to Quaternions in Blender.\n"
              "\n"
-             "   :param seq: size 3 or 4\n"
+             "   :arg seq: size 3 or 4\n"
              "   :type seq: :class:`Vector`\n"
-             "   :param angle: rotation angle, in radians\n"
+             "   :arg angle: rotation angle, in radians\n"
              "   :type angle: float\n"
              "\n"
              "   The constructor takes arguments in various forms:\n"

source/blender/python/mathutils/mathutils_Vector.c

@@ -3188,7 +3188,7 @@ PyDoc_STRVAR(vector_doc,
              "\n"
              "   This object gives access to Vectors in Blender.\n"
              "\n"
-             "   :param seq: Components of the vector, must be a sequence of at least two\n"
+             "   :arg seq: Components of the vector, must be a sequence of at least two\n"
              "   :type seq: sequence of numbers\n");
 PyTypeObject vector_Type = {
     PyVarObject_HEAD_INIT(NULL, 0)