Fixed warnings on RHEL (#1627) (#1630)

* reduce minimal requeriments

Signed-off-by: Alejandro Hernández Cordero <ahcorde@gmail.com>
(cherry picked from commit 088a605)

Co-authored-by: Alejandro Hernández Cordero <ahcorde@gmail.com>

zstd_vendor/CMakeLists.txt

@@ -6,7 +6,9 @@ find_package(ament_cmake_vendor_package REQUIRED)
 
 list(INSERT CMAKE_MODULE_PATH 0 "${CMAKE_CURRENT_SOURCE_DIR}/cmake/Modules")
 # We need at least VERSION 1.5.5, version check is done in Findzstd.cmake
-find_package(zstd 1.5.5 QUIET)
+# The platform with the oldest supported version is RHEL-9,
+# which has zstd 1.5.1.  Make sure we have at least that version.
+find_package(zstd 1.5.1 QUIET)
 
 ament_vendor(zstd_vendor
   SATISFIED ${zstd_FOUND}