Update dependency nanoc to v4.12.19

[renovate]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
nanoc (source)	4.12.18 -> 4.12.19

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Release Notes

nanoc/nanoc (nanoc)

v4.12.19

Compare Source

Fixes:

• Restored support for YAML aliases (#​1677) [zor-el]
• Fixed inadvertent reference to Nanoc:: namespace from within nanoc-cli gem (#​1673)

Enhancements:

• Made the default Rules file use #passthrough (#​1668) [Hendrik Jäger]
• Added support for slim 5.x (#​1675)
• Added support for psych 5.x (#​1674)
• Added source_code_uri metadata to gemspecs (#​1669) [Junichi Sato]

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