yaml/v2: suppress debug messages. #7900

Job	Run time
run-ubuntu-unit-tests (-DFLB_JEMALLOC=On, gcc)	19m 9s
run-ubuntu-unit-tests (-DFLB_JEMALLOC=On, clang)	19m 42s
run-ubuntu-unit-tests (-DFLB_JEMALLOC=Off, gcc)	17m 49s
run-ubuntu-unit-tests (-DFLB_JEMALLOC=Off, clang)	17m 15s
run-ubuntu-unit-tests (-DFLB_SMALL=On, gcc)	17m 53s
run-ubuntu-unit-tests (-DFLB_SMALL=On, clang)	18m 52s
run-ubuntu-unit-tests (-DSANITIZE_ADDRESS=On, gcc)	18m 20s
run-ubuntu-unit-tests (-DSANITIZE_ADDRESS=On, clang)	18m 18s
run-ubuntu-unit-tests (-DSANITIZE_UNDEFINED=On, gcc)	18m 31s
run-ubuntu-unit-tests (-DSANITIZE_UNDEFINED=On, clang)	17m 43s
run-ubuntu-unit-tests (-DFLB_COVERAGE=On, gcc)	52m 21s
run-ubuntu-unit-tests (-DFLB_SANITIZE_MEMORY=On, gcc)	17m 56s
run-ubuntu-unit-tests (-DFLB_SANITIZE_MEMORY=On, clang)	17m 56s
run-ubuntu-unit-tests (-DFLB_SANITIZE_THREAD=On, gcc)	18m 38s
run-ubuntu-unit-tests (-DFLB_SANITIZE_THREAD=On, clang)	18m 23s
run-macos-unit-tests (-DFLB_JEMALLOC=Off)	12m 56s
run-macos-unit-tests (-DFLB_SANITIZE_MEMORY=On)	12m 57s
run-macos-unit-tests (-DFLB_SANITIZE_THREAD=On)	19m 43s
Unit tests (matrix)	1s
	5h 54m 23s

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