Fix #143490: Missing uniform for POLYLINE_UNIFORM_COLOR gpu python API

Add vec4 color as uniform in PYDOC_BUILTIN_SHADER_DESCRIPTION for POLYLINE_UNIFORM_COLOR
builtin shader in accordance with gpu_shader_3D_polyline_info.hh.

Pull Request: https://projects.blender.org/blender/blender/pulls/143703

source/blender/python/gpu/gpu_py_shader.cc

@@ -59,7 +59,7 @@
   "   :Uniforms: vec2 viewportSize, float lineWidth\n" \
   "``POLYLINE_UNIFORM_COLOR``\n" \
   "   :Attributes: vec3 pos\n" \
-  "   :Uniforms: vec2 viewportSize, float lineWidth\n" \
+  "   :Uniforms: vec2 viewportSize, float lineWidth, vec4 color\n" \
   "``POINT_FLAT_COLOR``\n" \
   "   :Attributes: vec3 pos, vec4 color\n" \
   "   :Uniforms: float size\n" \