API Documentation: Add note to gpu.shader to explicitly set all uniforms

Fix #103176

Pull Request: https://projects.blender.org/blender/blender/pulls/146860

source/blender/python/gpu/gpu_py_shader.cc

@@ -1049,6 +1049,11 @@ PyDoc_STRVAR(
     "All built-in shaders have the ``mat4 ModelViewProjectionMatrix`` uniform.\n"
     "\n"
     "Its value must be modified using the :class:`gpu.matrix` module.\n"
+    "\n"
+    ".. important::\n"
+    "\n"
+    "   Shader uniforms must be explicitly initialized to avoid retaining values from previous "
+    "executions.\n"
     "\n" PYDOC_BUILTIN_SHADER_DESCRIPTION);
 static PyModuleDef pygpu_shader_module_def = {
     /*m_base*/ PyModuleDef_HEAD_INIT,