Bump @springio/asciidoctor-extensions in /docs #2905

Job	Run time
Test Against Snapshots / Test	48s
Build (ubuntu-latest, 17) / Build	34s
Build (windows-latest, 17) / Build	1m 50s
Deploy Artifacts / Deploy Artifacts	0s
Deploy Docs / Deploy Docs	0s
Perform Release	0s
	3m 12s

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