docs/fix syntax highlighting language

[thescientist13]

Related Issue

#1122

Got the syntax highlighting wrong, which is showing up in the build (though not breaking it)

Error: Unknown language: `sh` is not registered
    at Refractor.highlight (/Users/owenbuckley/Workspace/project-evergreen/greenwood/node_modules/refractor/core.js:115:13)
    at visitor (/Users/owenbuckley/Workspace/project-evergreen/greenwood/node_modules/@mapbox/rehype-prism/index.js:30:26)
    at overload (/Users/owenbuckley/Workspace/project-evergreen/greenwood/node_modules/unist-util-visit/index.js:27:12)
    at node (/Users/owenbuckley/Workspace/project-evergreen/greenwood/node_modules/unist-util-visit-parents/index.js:51:27)
    at children (/Users/owenbuckley/Workspace/project-evergreen/greenwood/node_modules/unist-util-visit-parents/index.js:77:42)
    at node (/Users/owenbuckley/Workspace/project-evergreen/greenwood/node_modules/unist-util-visit-parents/index.js:62:28)
    at children (/Users/owenbuckley/Workspace/project-evergreen/greenwood/node_modules/unist-util-visit-parents/index.js:77:42)
    at node (/Users/owenbuckley/Workspace/project-evergreen/greenwood/node_modules/unist-util-visit-parents/index.js:62:28)
    at visitParents (/Users/owenbuckley/Workspace/project-evergreen/greenwood/node_modules/unist-util-visit-parents/index.js:27:22)
    at visit (/Users/owenbuckley/Workspace/project-evergreen/greenwood/node_modules/unist-util-visit/index.js:22:3)
prerendering complete for page /plugins/adapter/.

Summary of Changes

1. fix it