GitHub CI: Workaround an issue on GitHub's macos runners

.github/workflows/install_dependencies_doc_macos.sh

@@ -1,3 +1,15 @@
 #!/usr/bin/env bash
 
+brew update
+
+# The install of 'texlive' may cause the install of a newer version of
+# 'python', which could fail because it cannot overwrite links for
+# older versions, due to an issue with the GitHub runner images:
+#   https://github.com/actions/runner-images/issues/9966
+# To avoid that, we unlink and install with overwrite:
+#
+for python_package in $(brew list | grep python@); do
+    brew unlink ${python_package} && brew link --overwrite ${python_package}
+done
+
 brew install texlive