**Title:**
Remove the `canonicalURL` field from demo metadata.

**Summary:**
This PR removes the `canonicalURL` field from existing demo metadata.
The `canonicalURL` field has been superseded by the (autogenerated)
`slug` field as of #1228.

**Relevant references:**
None.

**Possible Drawbacks:**
None.

**Related GitHub Issues:**
None.

---

**Detailed Changes:**
1. Fixed the `$id` reference in `demo.metadata.schema.0.1.3.json`. 
2. Added `demo.metadata.schema.0.1.4.json` which removes the
`canonicalURL` field.
3. Updated the example metadata in `demonstrations_metadata.md`.
4. Removed the `canonicalURL` field from existing demo metadata (and
adjusted `dateOfLastModification`).
5. Deleted the obsolete `update_metadata.py` script.

**Merge Checklist:**
* [x] Delete the "Build Website - Text (Test)" GHA workflow which was
added for testing purposes.

**Verification:**

The generated `metadata.json` file in the Glass Onion bucket no longer
has any `canonicalURL` fields:

<details><summary><tt>metadata.json</tt> Snippet</summary>
<p>

```json
[
  {
    "authors": [
      {
        "username": "whatsis"
      }
    ],
    "basedOnPapers": [],
    "categories": [
      "Quantum Computing",
      "How-to"
    ],
    "dateOfLastModification": "2024-10-07T00:00:00+00:00",
    "dateOfPublication": "2024-10-01T00:00:00+00:00",
    "doi": "",
    "previewImages": [
      {
        "type": "thumbnail",
        "uri": "/_static/demo_thumbnails/regular_demo_thumbnails/thumbnail_how_to_use_noise_models.png"
      },
      {
        "type": "large_thumbnail",
        "uri": "/_static/demo_thumbnails/large_demo_thumbnails/thumbnail_large_how_to_use_noise_models.png"
      }
    ],
    "referencedByPapers": [],
    "references": [],
    "relatedContent": [
      {
        "id": "tutorial_noisy_circuits",
        "type": "demonstration",
        "weight": 1
      }
    ],
    "seoDescription": "Learn how noise models can be built and inserted into a quantum circuit in PennyLane.",
    "slug": "tutorial_how_to_use_noise_models",
    "tags": [],
    "title": "How to use noise models in PennyLane"
  },
  ...
]
```

</p>
</details>

…namic circuits" (#1185)

**Title:**
Constant-depth preparation of matrix product states with dynamic
circuits

**Summary:**
Matrix product states (MPS) form an important class of quantum many-body
states. Preparing them is an important subroutine for any algorithm that
want to use MPS as an initial state, for example. A recent paper, on
which this demo is based, and which it is following closely, generalized
a method that reduces the depth of such a preparation circuit to
constant scaling, by using auxiliary qubits and dynamic quantum circuits
(mid-circuit measurements together with classical feedforward).
We here focus on the simplest scenario in the main text of the paper,
and implement a simple example in code.
The implemented MPS has a parameter controlling the correlation length
of the prepared state, which we verify explicitly.

**Relevant references:**
https://arxiv.org/pdf/2404.16083
https://arxiv.org/pdf/quant-ph/0501096
https://journals.aps.org/prxquantum/pdf/10.1103/PRXQuantum.4.020315

**Possible Drawbacks:**

**Related GitHub Issues:**

----
If you are writing a demonstration, please answer these questions to
facilitate the marketing process.

* GOALS — Why are we working on this now?

Mid-circuit measurements recently are/were a focus point in PennyLane.
MPS states are used in some quantum chemistry algorithms as initial
state.


* AUDIENCE — Who is this for?

  Researchers in quantum algorithms


* KEYWORDS — What words should be included in the marketing post?

TBD

* Which of the following types of documentation is most similar to your
file?
(more details
[here](https://www.notion.so/xanaduai/Different-kinds-of-documentation-69200645fe59442991c71f9e7d8a77f8))
    
- [ ] Tutorial
- [x] Demo
- [ ] How-to

[sc-64275]

---------

Co-authored-by: Korbinian Kottmann <[email protected]>
Co-authored-by: Ivana Kurečić <[email protected]>