fix(ci): Remove Debian 11 & add Debian 13 in the test matrix

[damacus]

Description

• Remove unreleased section
• Remove Debian 11 & add Debian 13 in the test matrix
• Fix markdownlint in CHANGELOG

Issues Resolved

List any existing issues this PR resolves

Check List

• A summary of changes made is included in the CHANGELOG under ## Unreleased
• New functionality includes testing.
• New functionality has been documented in the README if applicable.

[github-actions]

Slowest examples

Top 10 slowest examples (3.21 seconds, 15.61% of total time)

Example	Description	Time in seconds
spec/resources/mod_spec.rb:166	apache2_install mod_ldap outputs template correctly	0.51264
spec/resources/mod_auth_cas_spec.rb:27	apache2_mod_auth_cas ubuntu is expected to enable apache2_module "auth_cas"	0.4653
spec/libraries/pid_file_spec.rb:15	#apache_pid_file with fedora family is expected to write log "/var/run/httpd/httpd.pid"	0.3746
spec/libraries/package_helpers_spec.rb:97	#default_apache_pkg with Debian is expected to write log "apache2"	0.36155
spec/libraries/log_dir_spec.rb:35	#log_dir with arch is expected to write log "/var/log/httpd"	0.30747
spec/libraries/devel_package_spec.rb:26	#apache_devel_package suse is expected to write log "apache2-devel"	0.26884
spec/resources/conf_spec.rb:34	apache2_install install an apache2_module with default properties Creates the ports template	0.23575
spec/resources/mod_auth_cas_spec.rb:55	apache2_mod_auth_cas ubuntu is expected to render file "/etc/apache2/mods-available/auth_cas.conf"	0.2302
spec/resources/default_site_spec.rb:20	apache2_install Enable the default site Creates the default site template	0.22974
spec/resources/mod_auth_cas_spec.rb:55	apache2_mod_auth_cas ubuntu is expected to render file "/etc/apache2/mods-available/auth_cas.conf"	0.22973