CI: force updating python3 symlink in opensuse-15 container image

The python3-base package installs a symlink pointing to python3.6.

Author: mgorny

ci/opensuse-15.docker

@@ -4,4 +4,4 @@
 
 # 20240817
 FROM opensuse/leap:latest
-RUN zypper --non-interactive install python311 python311-pip python311-devel gcc ninja git patchelf cmake && zypper clean --all && ln -s python3.11 /usr/bin/python3
+RUN zypper --non-interactive install python311 python311-pip python311-devel gcc ninja git patchelf cmake && zypper clean --all && ln -sf python3.11 /usr/bin/python3