[SYCL][DOC] Update extension template date (#8059)

Author: gmlueck

sycl/doc/extensions/template.asciidoc

@@ -20,7 +20,7 @@
 == Notice
 
 [%hardbreaks]
-Copyright (C) 2022-2022 Intel Corporation.  All rights reserved.
+Copyright (C) 2023-2023 Intel Corporation.  All rights reserved.
 
 Khronos(R) is a registered trademark and SYCL(TM) and SPIR(TM) are trademarks
 of The Khronos Group Inc.  OpenCL(TM) is a trademark of Apple Inc. used by