After-merge fix: Correct a copyright statement

In the merge c51f85f8
the files row0trunc.cc and read0read.cc were not supposed
to be changed in MariaDB 10.3.

The row0trunc.cc code that was changed in MariaDB 10.2
commit 3db94d24 does not exist,
because it was removed earlier in 10.3
commit 5a1868b5.

When it comes to read0read.cc, as explained in the 10.2
commit e0271a7b
the code had been moved to trx0sys.h in 10.3. In
10.3 commit 380069c2
appproriate mutex protection was added to checking the
transaction system state. The assertion expression was
properly updated in the earlier merge
commit acf6f92a.

storage/innobase/read/read0read.cc

 /*****************************************************************************
 
 Copyright (c) 1996, 2015, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2019, MariaDB Corporation.
+Copyright (c) 2018, 2019, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software