test(pnpm): Drop the unsupported workspaces property

When running `pnpm` in the project directory of the `workspaces`
project, it outputs the warning [^1]. Remove the `workspaces` property,
to fix that warning.

[^1]: `The "workspaces" field in package.json is not supported by pnpm.
     Create a "pnpm-workspace.yaml" file instead.`

Signed-off-by: Frank Viernau <frank_viernau@epam.com>

plugins/package-managers/node/src/funTest/assets/projects/synthetic/pnpm/workspaces/package.json

@@ -6,10 +6,6 @@
  "author": "Marcel Bochtler",
  "license": "MIT",
  "main": "index.js",
- "workspaces": [
- "src/app",
- "src/packages/**"
- ],
  "engines": {
  "node": ">16.0.0",
  "pnpm": ">=5"