Documentation: *san: drop "the" from article titles

Drop "the" from the titles of documentation articles for KASAN, KCSAN,
and KMSAN, as it is redundant.

Also add SPDX-License-Identifier for kasan.rst.

Link: https://lkml.kernel.org/r/1c4eb354a3a7b8ab56bf0c2fc6157c22050793ca.1696605143.git.andreyknvl@google.comSigned-off-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: kernel test robot <lkp@intel.com>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Documentation/dev-tools/kasan.rst

-The Kernel Address Sanitizer (KASAN)
-====================================
+.. SPDX-License-Identifier: GPL-2.0
+.. Copyright (C) 2023, Google LLC.
+
+Kernel Address Sanitizer (KASAN)
+================================
 
 Overview
 --------

Documentation/dev-tools/kcsan.rst

 .. SPDX-License-Identifier: GPL-2.0
 .. Copyright (C) 2019, Google LLC.
 
-The Kernel Concurrency Sanitizer (KCSAN)
-========================================
+Kernel Concurrency Sanitizer (KCSAN)
+====================================
 
 The Kernel Concurrency Sanitizer (KCSAN) is a dynamic race detector, which
 relies on compile-time instrumentation, and uses a watchpoint-based sampling

Documentation/dev-tools/kmsan.rst

 .. SPDX-License-Identifier: GPL-2.0
 .. Copyright (C) 2022, Google LLC.
 
-===================================
-The Kernel Memory Sanitizer (KMSAN)
-===================================
+===============================
+Kernel Memory Sanitizer (KMSAN)
+===============================
 
 KMSAN is a dynamic error detector aimed at finding uses of uninitialized
 values. It is based on compiler instrumentation, and is quite similar to the