CHANGELOG: update for 1.9.1-rc0 #135

Job	Run time
coverage-test	7m 29s
coverity-test	0s
generic-build-test (ubuntu-18.04, gcc)	7m 15s
fuzzing-test	4m 41s
generic-build-test (ubuntu-18.04, clang)	6m 13s
generic-build-test (ubuntu-20.04, gcc)	7m 1s
generic-build-test (ubuntu-20.04, clang)	5m 45s
generic-build-test (fedora-30, gcc)	7m 10s
generic-build-test (fedora-30, clang)	6m 32s
generic-build-test (opensuse-leap, gcc)	7m 2s
generic-build-test (opensuse-leap, clang)	6m 14s
generic-build-test (ubuntu-22.04, gcc)	44m 46s
	1h 50m 8s

Provide feedback