fix key hashing for v5 / v6 signatures #3744

Job	Run time
cmake-offline-googletest	4m 20s
cmake-offline-googletest-src	4m 7s
system-sexpp, sexpp shared libs on, rnp shared libs on	2m 47s
package-source	47s
system-sexpp, sexpp shared libs on, rnp shared libs off	2m 55s
system-sexpp, sexpp shared libs off, rnp shared libs on	3m 1s
ubuntu-latest [CC gcc; botan; shared libs on; GnuPG stable]	4m 27s
system-sexpp, sexpp shared libs off, rnp shared libs off	3m 2s
ubuntu-latest [CC clang; botan; shared libs on; GnuPG stable]	4m 34s
ubuntu-latest [CC gcc; openssl; shared libs on; GnuPG stable]	4m 0s
ubuntu-latest [CC clang; openssl; shared libs on; GnuPG stable]	4m 4s
ubuntu-20.04 [CC gcc; openssl; shared libs on; GnuPG stable]	4m 1s
ubuntu-latest [CC gcc; botan; shared libs off; GnuPG stable]	4m 16s
package	56s
debian-tests	13s
	47m 30s

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