Fix formatting of warning block in `README.md` #675

Job	Run time
Linux - bootstrap-ubi.sh - no tag	5s
Linux - bootstrap-ubi.sh - v0.1.1	5s
Alpine Linux (ash) - bootstrap-ubi.sh - no tag	6s
Alpine Linux (ash) - bootstrap-ubi.sh - v0.1.1	9s
macOS - bootstrap-ubi.sh - no tag	5s
macOS - bootstrap-ubi.sh - v0.1.1	5s
Windows - bootstrap-ubi.ps1 - no tag	14s
	49s

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