Update changelog for 7.5.21 #161

Job	Run time
lint-unit / markdown-link-check	19s
lint-unit / cookstyle	33s
lint-unit / markdownlint-cli2	6s
lint-unit / rspec	36s
lint-unit / yamllint	9s
lint-unit / check-metadata	0s
integration (centos-stream-8, default)	1m 9s
integration (debian-10, default)	1m 12s
integration (debian-10, cacher)	1m 21s
integration (debian-10, compile-time)	1m 14s
integration (debian-10, unattended-upgrades)	1m 20s
integration (debian-11, default)	1m 9s
integration (debian-11, cacher)	1m 17s
integration (debian-11, compile-time)	1m 12s
integration (debian-11, unattended-upgrades)	1m 12s
integration (ubuntu-1804, default)	1m 14s
integration (ubuntu-1804, cacher)	1m 22s
integration (ubuntu-1804, compile-time)	1m 10s
integration (ubuntu-1804, unattended-upgrades)	1m 23s
integration (ubuntu-2004, default)	1m 11s
integration (ubuntu-2004, cacher)	1m 22s
integration (ubuntu-2004, compile-time)	1m 10s
integration (ubuntu-2004, unattended-upgrades)	1m 30s
integration (ubuntu-2204, default)	1m 13s
integration (ubuntu-2204, cacher)	1m 27s
integration (ubuntu-2204, compile-time)	1m 19s
integration (ubuntu-2204, unattended-upgrades)	1m 20s
	28m 30s

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