Remove redundant LICENSE.txt download link from docs/README.rst license notice

Author: chenyunliang520

docs/README.rst

@@ -8,8 +8,6 @@ GaussDB documentation build
    **License**: This documentation is part of the **gaussdb** project and is licensed under the
    `GNU Lesser General Public License v3.0 (LGPL v3)`_.
 
-   See the :download:`LICENSE.txt <../LICENSE.txt>` file in the project root for details.
-
 .. _GNU Lesser General Public License v3.0 (LGPL v3): https://www.gnu.org/licenses/lgpl-3.0.en.html