The CMake prepares file AUTHORS for packing.
It only contains one line, and isn't packed in any upstream-produced packagess.
I don't find it useful and since upstream doesn't pack it either, stop packing it here.

The README file contains infromation on how to build the project from sources, and thus isn't useful for the end users.

On the other hand, the README-MySQL isn't prepared for packing by CMake, but contains useful information about the software usage and it is package in upstream-produced packages.

Offered upstream:
https://github.com/codership/galera/pull/666
https://groups.google.com/g/codership-team/c/Cn4UO3MkNQs

--- galera-26.4.18/CMakeLists.txt	2024-06-09 04:54:56.281408893 +0200
+++ galera-26.4.18/CMakeLists.txt_patched	2024-06-09 06:52:58.093217968 +0200
@@ -118,9 +118,8 @@ endif()
 
 if (NOT ${CMAKE_SYSTEM_NAME} MATCHES ".*BSD")
   install(FILES
-    ${PROJECT_SOURCE_DIR}/AUTHORS
     ${PROJECT_SOURCE_DIR}/COPYING
-    ${PROJECT_SOURCE_DIR}/README
+    ${PROJECT_SOURCE_DIR}/scripts/packages/README-MySQL
     DESTINATION ${INSTALL_DOCDIR} )
   install(FILES ${PROJECT_SOURCE_DIR}/asio/LICENSE_1_0.txt
     DESTINATION ${INSTALL_DOCDIR}