Revert "Initialize Quaternion variant with identity"

This reverts commit 3797928.

This may be correct, but it breaks compatibility so it shouldn't be
cherry-picked to stable branches.

Author: akien-mga

core/variant/variant_internal.h

@@ -54,9 +54,6 @@ class VariantInternal {
 			case Variant::TRANSFORM2D:
 				init_transform2d(v);
 				break;
-			case Variant::QUATERNION:
-				init_quaternion(v);
-				break;
 			case Variant::AABB:
 				init_aabb(v);
 				break;
@@ -226,7 +223,7 @@ class VariantInternal {
 
 	// Should be in the same order as Variant::Type for consistency.
 	// Those primitive and vector types don't need an `init_` method:
-	// Nil, bool, float, Vector2/i, Rect2/i, Vector3/i, Plane, RID.
+	// Nil, bool, float, Vector2/i, Rect2/i, Vector3/i, Plane, Quat, RID.
 	// Object is a special case, handled via `object_assign_null`.
 	_FORCE_INLINE_ static void init_string(Variant *v) {
 		memnew_placement(v->_data._mem, String);
@@ -237,10 +234,6 @@ class VariantInternal {
 		memnew_placement(v->_data._transform2d, Transform2D);
 		v->type = Variant::TRANSFORM2D;
 	}
-	_FORCE_INLINE_ static void init_quaternion(Variant *v) {
-		memnew_placement(v->_data._mem, Quaternion);
-		v->type = Variant::QUATERNION;
-	}
 	_FORCE_INLINE_ static void init_aabb(Variant *v) {
 		v->_data._aabb = (AABB *)Variant::Pools::_bucket_small.alloc();
 		memnew_placement(v->_data._aabb, AABB);