BUG: Nutanix fix for wrong section name from special agent after last commits

[Yogibaer75]

General information

Nutanix Cluster checks are getting no data as the section providing the data changed names after the last commit https://github.com/Checkmk/checkmk/commit/3faacc012ca9ad8e66285ce62d221e79df56e43c before --> prism_info now --> prism_cluster This is fixed with my PR. It changes the internal section as it is needed.