Align ripgrep Linux install hint

[GreyforgeLabs]

Summary

• Update the Linux ripgrep install hint to match the sudo apt/dnf commands used by cortex debug ripgrep --install.

Fixes PlatformNetwork/bounty-challenge#53124

Validation

• cargo fmt --package cortex-cli --check
• git diff --check
• cargo check -p cortex-cli --no-default-features --features cortex-tui

[greptile-apps]

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