Remove circle/diamond and NodePath String constants

They were introduced in #14704 but need more discussion IMO,
they don't strike me as core features that would have to be
registered in Variant directly.

Moreover, they currently break the documentation XML as string
constants end up encoded as e.g. `value=""..""`.

core/variant_call.cpp

@@ -1925,18 +1925,6 @@ void register_variant_methods() {
 	_VariantCall::add_variant_constant(Variant::PLANE, "Z", Plane(Vector3(0, 0, 1), 0));
 
 	_VariantCall::add_variant_constant(Variant::QUAT, "IDENTITY", Quat(0, 0, 0, 1));
-
-	CharType black_circle[2] = { 0x25CF, 0 };
-	_VariantCall::add_variant_constant(Variant::STRING, "BLACK_CIRCLE", String(black_circle));
-	CharType white_circle[2] = { 0x25CB, 0 };
-	_VariantCall::add_variant_constant(Variant::STRING, "WHITE_CIRCLE", String(white_circle));
-	CharType black_diamond[2] = { 0x25C6, 0 };
-	_VariantCall::add_variant_constant(Variant::STRING, "BLACK_DIAMOND", String(black_diamond));
-	CharType white_diamond[2] = { 0x25C7, 0 };
-	_VariantCall::add_variant_constant(Variant::STRING, "WHITE_DIAMOND", String(white_diamond));
-
-	_VariantCall::add_variant_constant(Variant::NODE_PATH, "CURRENT", String("."));
-	_VariantCall::add_variant_constant(Variant::NODE_PATH, "PARENT", String(".."));
 }
 
 void unregister_variant_methods() {