Change version to 5.1 in comments in powershell5 recipe

[jugatsu]

Description

• Update powershell version to 5.1 in comments.

[stuartpreston]

@jugatsu Thanks for the effort, the maintainers will update the changelog using a changelog generator at release time. We're still working through some build issues first but will get a release out asap.

[stuartpreston]

@jugatsu Actually I see you're squeezing in a change to the powershell 5 recipe. Can you revert your commits involving CHANGELOG.md and force push and we'll get the rest merged.

[jugatsu]

@stuartpreston Done.

[tas50]

Thanks