Documentation: ubsan: drop "the" from article title

Drop "the" from the title of the documentation article for UBSAN, as it is
redundant.

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

Link: https://lkml.kernel.org/r/5fb11a4743eea9d9232a5284dea0716589088fec.1698161845.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <[email protected]>
Reviewed-by: Marco Elver <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: xairy

Documentation/dev-tools/ubsan.rst

@@ -1,5 +1,7 @@
-The Undefined Behavior Sanitizer - UBSAN
-========================================
+.. SPDX-License-Identifier: GPL-2.0
+
+Undefined Behavior Sanitizer - UBSAN
+====================================
 
 UBSAN is a runtime undefined behaviour checker.