test(monorepo): use a plugin that has required plugin options

Author: apaleslimghost

plugins/monorepo/test/files/invalid/c/.toolkitrc.yml

@@ -1,4 +1,4 @@
 plugins:
-  - @dotcom-tool-kit/hako
+  - '@dotcom-tool-kit/docker'
 
-# deliberately missing task options to fail validation
+# deliberately missing plugin options to fail validation

plugins/monorepo/test/load-workspace-configs.test.ts

@@ -31,14 +31,21 @@ describe('LoadWorkspaceConfigs', () => {
         cwd: path.relative(process.cwd(), path.resolve(__dirname, './files/invalid'))
       })
     ).rejects.toMatchInlineSnapshot(`
-      AggregateError "1 error loading .toolkitrc.yml in workspace packages" {
+      AggregateError "2 errors loading .toolkitrc.yml in workspace packages" {
         "errors": [
           "@monorepo-plugin-tests/b → ToolKitError" "There are options in your .toolkitrc.yml that aren't what Tool Kit expected." {
             "details": "Please update the options so that they are the expected types.
        !  2 issues in @dotcom-tool-kit/serverless:
       - Required at "awsAccountId"
       - Required at "systemCode"
 
+      You can refer to the README for the plugin for examples and descriptions of the options used.",
+          },
+          "@monorepo-plugin-tests/c → ToolKitError" "There are options in your .toolkitrc.yml that aren't what Tool Kit expected." {
+            "details": "Please update the options so that they are the expected types.
+       !  1 issue in @dotcom-tool-kit/docker:
+      - Required at "images"
+
       You can refer to the README for the plugin for examples and descriptions of the options used.",
           },
         ],