CHANGELOG: update for 1.9.1-rc0 #460

Job	Run time
generic-build-test (ubuntu-18.04, gcc)	7m 24s
generic-build-test (ubuntu-18.04, clang)	6m 25s
coverage-test	7m 16s
generic-build-test (ubuntu-20.04, gcc)	6m 50s
fuzzing-test	4m 27s
generic-build-test (ubuntu-20.04, clang)	6m 3s
generic-build-test (fedora-30, gcc)	7m 31s
coverity-test	0s
generic-build-test (fedora-30, clang)	6m 32s
generic-build-test (opensuse-leap, gcc)	7m 7s
generic-build-test (opensuse-leap, clang)	6m 9s
generic-build-test (ubuntu-22.04, gcc)	44m 37s
	1h 50m 21s

Provide feedback