Remove unneeded psych gem

[moleske]

• in Use newer Psych rather than ruby's built in YAML #2807 we manually set psych so we could resolve numbers with commas in space manifests get parsed as an integer, not a string #2193
• the newer psych is available as a default gem in ruby 3.2

We could keep psych in the gemfile if we feel value in staying on the latest version psych instead of what version of psych ruby provides. I don't have strong feelings either way (well strong enough to make a pr, not strong enough to advocate deeply)

The key thing we needed to resolve the issue was strict_integer: true in all the parse commands, nothing else from psych we cared all that much about

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[philippthun]

I also favor removing this, as long as we don't need a specific (newer) version.