Enforce use of bool literals instead of integers

Using clang-tidy's `modernize-use-bool-literals`.
https://clang.llvm.org/extra/clang-tidy/checks/modernize-use-bool-literals.html

scene/2d/polygon_2d.cpp

@@ -723,7 +723,7 @@ void Polygon2D::_bind_methods() {
 
 Polygon2D::Polygon2D() {
 
-	invert = 0;
+	invert = false;
 	invert_border = 100;
 	antialiased = false;
 	tex_rot = 0;