optional_plugins/spawner_remote: add missing manifest to include VERSION

[clebergnu]

Without this, building packages (such as wheels) will fail for the plugin.

[mr-avocado]

Dear contributor,
Avocado is currently under sprint #103, which is due to release an LTS (Long Term Stability) release.
Please avoid merging changes that do not fall into these categories:

• Bug fixes
• Usability Improvements
• Documentation updates

As for the Avocado utility modules (“avocado.utils”) it is OK to introduce new functionality,
but changes to the existing APIs (including interface and behavior) should be avoided.
These kind of changes should wait until sprint #104.

[clebergnu]

For the record, it's unfortunately a silent failure and can be seen here:

2023-12-22T14:57:52.8774519Z removing 'avocado-framework-plugin-spawner-remote-102.0' (and everything under it)
2023-12-22T14:57:52.9196845Z * Building wheel from sdist
2023-12-22T14:57:52.9197541Z * Creating venv isolated environment...
2023-12-22T14:57:56.4029440Z * Installing packages in isolated environment... (setuptools >= 40.8.0, wheel)
2023-12-22T14:57:57.9448231Z * Getting build dependencies for wheel...
2023-12-22T14:57:58.0480785Z Traceback (most recent call last):
2023-12-22T14:57:58.0482986Z   File "/home/runner/.local/lib/python3.12/site-packages/pyproject_hooks/_in_process/_in_process.py", line 353, in <module>
2023-12-22T14:57:58.0484631Z     main()
2023-12-22T14:57:58.0486808Z   File "/home/runner/.local/lib/python3.12/site-packages/pyproject_hooks/_in_process/_in_process.py", line 335, in main
2023-12-22T14:57:58.0488759Z     json_out['return_val'] = hook(**hook_input['kwargs'])
2023-12-22T14:57:58.0489683Z                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2023-12-22T14:57:58.0491434Z   File "/home/runner/.local/lib/python3.12/site-packages/pyproject_hooks/_in_process/_in_process.py", line 118, in get_requires_for_build_wheel
2023-12-22T14:57:58.0492931Z     return hook(config_settings)
2023-12-22T14:57:58.0493450Z            ^^^^^^^^^^^^^^^^^^^^^
2023-12-22T14:57:58.0495832Z   File "/tmp/build-env-51haf5y4/lib/python3.12/site-packages/setuptools/build_meta.py", line 325, in get_requires_for_build_wheel
2023-12-22T14:57:58.0497622Z     return self._get_build_requires(config_settings, requirements=['wheel'])
2023-12-22T14:57:58.0498555Z            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2023-12-22T14:57:58.0500243Z   File "/tmp/build-env-51haf5y4/lib/python3.12/site-packages/setuptools/build_meta.py", line 295, in _get_build_requires
2023-12-22T14:57:58.0501429Z     self.run_setup()
2023-12-22T14:57:58.0502662Z   File "/tmp/build-env-51haf5y4/lib/python3.12/site-packages/setuptools/build_meta.py", line 480, in run_setup
2023-12-22T14:57:58.0504180Z     super(_BuildMetaLegacyBackend, self).run_setup(setup_script=setup_script)
2023-12-22T14:57:58.0505268Z   File "/tmp/build-env-51haf5y4/lib/python3.12/site-packages/setuptools/build_meta.py", line 311, in run_setup
2023-12-22T14:57:58.0506135Z     exec(code, locals())
2023-12-22T14:57:58.0506440Z   File "<string>", line 29, in <module>
2023-12-22T14:57:58.0507349Z FileNotFoundError: [Errno 2] No such file or directory: '/tmp/build-via-sdist-y4elmtsk/avocado-framework-plugin-spawner-remote-102.0/VERSION'

[richtja]

LGTM, thanks