Update QAOA-Maxcut demo with a few good practices (#1251)

**Title:**

**Summary:**

Just updating the MaxCut demo with a few tiny changes that incorporate
good practices in Python/PennyLane, which have changed since the
creation back in 2019.

**Relevant references:**

**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?

*Eg. Promote a new PL feature or show a PL implementation of a recent
paper.*


* AUDIENCE — Who is this for?

*Eg. Chemistry researchers, PL educators, beginners in quantum
computing.*


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


* 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
- [ ] Demo
- [ ] How-to

demonstrations/tutorial_qaoa_maxcut.metadata.json

@@ -6,7 +6,7 @@
         }
     ],
     "dateOfPublication": "2019-10-11T00:00:00+00:00",
-    "dateOfLastModification": "2024-11-06T00:00:00+00:00",
+    "dateOfLastModification": "2024-11-20T00:00:00+00:00",
     "categories": [
         "Optimization"
     ],