Upgrade pry-shell gem to version 0.5.1

What does this MR do and why?

This version of the pry-shell gem fixes the following issues;

• Using Ctrl-D when in a session causes hang
• killing connected process breaks terminal
• using quit hangs the session

And introduces the following feature;

• Add Vim key bindings to Main Menu

Changes are here: https://github.com/meinac/pry-shell/compare/v0.5.0...v0.5.1

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.