Fix llvm compilation by adding missing override

modules/openxr/extensions/openxr_vulkan_extension.h

@@ -55,9 +55,9 @@ public:
 	virtual void on_instance_created(const XrInstance p_instance) override;
 	virtual void *set_session_create_and_get_next_pointer(void *p_next_pointer) override;
 
-	virtual bool create_vulkan_instance(const VkInstanceCreateInfo *p_vulkan_create_info, VkInstance *r_instance);
-	virtual bool get_physical_device(VkPhysicalDevice *r_device);
-	virtual bool create_vulkan_device(const VkDeviceCreateInfo *p_device_create_info, VkDevice *r_device);
+	virtual bool create_vulkan_instance(const VkInstanceCreateInfo *p_vulkan_create_info, VkInstance *r_instance) override;
+	virtual bool get_physical_device(VkPhysicalDevice *r_device) override;
+	virtual bool create_vulkan_device(const VkDeviceCreateInfo *p_device_create_info, VkDevice *r_device) override;
 
 	virtual void get_usable_swapchain_formats(Vector<int64_t> &p_usable_swap_chains) override;
 	virtual String get_swapchain_format_name(int64_t p_swapchain_format) const override;