Merge pull request #10832 from Icinga/fix-openSUSE15.6-GHA

Fix openSUSE 15.6 GitHub actions

Author: Al2Klimov

.github/workflows/linux.bash

@@ -61,7 +61,7 @@ case "$DISTRO" in
     ;;
 
   *suse*)
-    zypper in -y bison ccache cmake flex gcc-c++ ninja rpm-config-SUSE \
+    zypper in -y --allow-downgrade bison ccache cmake flex gcc-c++ ninja rpm-config-SUSE \
       {lib{edit,mariadb,openssl},ncurses,postgresql,systemd,protobuf}-devel \
       libboost_{context,coroutine,filesystem,iostreams,program_options,regex,system,test,thread}-devel
     ;;