quarto: write-manifest with a Quarto file cannot locate manifest.json

[aronatkins]

Given a simple Quarto document in a directory by itself named index.qmd:

---
title: simple
---

i am simple

Attempting to construct a manifest for this file errs.

rsconnect write-manifest quarto index.qmd
Checking arguments...                            [OK]
Inspecting Quarto project...                     [OK]
Creating manifest.json...                        Traceback (most recent call last):
  File "DOCUMENT_DIRECTORY/env/lib/python3.11/site-packages/rsconnect/actions.py", line 87, in cli_feedback
    yield
  File "DOCUMENT_DIRECTORY/env/lib/python3.11/site-packages/rsconnect/main.py", line 1812, in write_manifest_quarto
    write_quarto_manifest_json(
  File "DOCUMENT_DIRECTORY/env/lib/python3.11/site-packages/rsconnect/bundle.py", line 2050, in write_quarto_manifest_json
    write_manifest_json(manifest_path, manifest)
  File "DOCUMENT_DIRECTORY/env/lib/python3.11/site-packages/rsconnect/bundle.py", line 2057, in write_manifest_json
    with open(manifest_path, "w") as f:
         ^^^^^^^^^^^^^^^^^^^^^^^^
NotADirectoryError: [Errno 20] Not a directory: 'index.qmd/manifest.json'
[ERROR]
Internal error: [Errno 20] Not a directory: 'index.qmd/manifest.json'

This appears to be because we have two implementations of write_quarto_manifest_json() and they have deviated.

https://github.com/rstudio/rsconnect-python/blob/add8610d1c16597756dc6f04b06150d10d1fa674/rsconnect/actions.py#L494-L538

https://github.com/rstudio/rsconnect-python/blob/add8610d1c16597756dc6f04b06150d10d1fa674/rsconnect/bundle.py#L2017-L2050

The first implementation, in actions.py, contains #254, while the bundle.py implementation does not. Likely overlooked in #244