Style: clang-format: Disable KeepEmptyLinesAtTheStartOfBlocks

Which means that reduz' beloved style which we all became used to
will now be changed automatically to remove the first empty line.

This makes us lean closer to 1TBS (the one true brace style) instead
of hybridating it with some Allman-inspired spacing.

There's still the case of braces around single-statement blocks that
needs to be addressed (but clang-format can't help with that, but
clang-tidy may if we agree about it).

Part of #33027.

modules/csg/csg.h

@@ -44,7 +44,6 @@
 #include "scene/resources/material.h"
 
 struct CSGBrush {
-
 	struct Face {
 		Vector3 vertices[3];
 		Vector2 uvs[3];
@@ -65,7 +64,6 @@ struct CSGBrush {
 };
 
 struct CSGBrushOperation {
-
 	enum Operation {
 		OPERATION_UNION,
 		OPERATION_INTERSECTION,
@@ -75,7 +73,6 @@ struct CSGBrushOperation {
 	void merge_brushes(Operation p_operation, const CSGBrush &p_brush_a, const CSGBrush &p_brush_b, CSGBrush &r_merged_brush, float p_vertex_snap);
 
 	struct MeshMerge {
-
 		struct Face {
 			bool from_b;
 			bool inside;
@@ -156,7 +153,6 @@ struct CSGBrushOperation {
 	};
 
 	struct Build2DFaces {
-
 		struct Vertex2D {
 			Vector2 point;
 			Vector2 uv;