build(deps): bump docker/metadata-action from 5.5.1 to 5.6.1 #745

Job	Run time
changes	2s
prechecks / validate	42s
prechecks / bootstrap-dev-rhel8	4m 26s
prechecks / import-check	2m 47s
prechecks / style	55s
prechecks / audit / package-audits (windows-latest, powershell Invoke-Expression -Command "./share/spack/qa/windows_t...	5m 16s
prechecks / audit / package-audits (ubuntu-latest, bash)	8m 37s
prechecks / audit / package-audits (macos-latest, bash)	5m 32s
all-prechecks	0s
unit-tests	0s
bootstrap	0s
coverage	0s
all	0s
	28m 17s

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