CHANGELOG: update for 1.9.1-rc0 #134

Job	Run time
coverity-test	0s
coverage-test	7m 12s
generic-build-test (ubuntu-18.04, gcc)	7m 21s
fuzzing-test	4m 30s
generic-build-test (ubuntu-18.04, clang)	6m 15s
generic-build-test (ubuntu-20.04, gcc)	6m 50s
generic-build-test (ubuntu-20.04, clang)	6m 0s
generic-build-test (fedora-30, gcc)	7m 6s
generic-build-test (fedora-30, clang)	6m 35s
generic-build-test (opensuse-leap, gcc)	6m 55s
generic-build-test (opensuse-leap, clang)	6m 8s
generic-build-test (ubuntu-22.04, gcc)	44m 32s
	1h 49m 24s

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