Tests scoping down SentenceSpacing somewhat

What does this MR do?

tl;dr Adds a scope (https://vale.sh/docs/topics/scoping/#markup) to SentenceSpacing.yml, though I want a second opinion on whether I've added the correct one. Includes instructions on how to reproduce.

@mwoolf pinged me this morning with a failing pipeline in !159440, saying it was a false positive, and he was right. The SentenceSpacing.yml rule was tripping up on this (correctly marked up) code example:

from django.db import models
class Animal(models.Model):
    name = models.CharField(max_length=200)
    number_of_legs = models.IntegerField(default=2) # 's.I' was flagged here
    dangerous = models.BooleanField(default=False)

I've been staring at it, asking myself why this got flagged. I kept reading the rule contents over and over before I spotted the ABSENCE of something. Don't ask how long it took me to spot there's no scope in the file:

extends: existence
message: "Use exactly one space between sentences and clauses. Check '%s' for spacing problems."
link: https://docs.gitlab.com/ee/development/documentation/styleguide/index.html#punctuation
level: error
nonword: true
tokens:
  - '[a-z][.?!,][A-Z]'
  - '[\w.?!,\(\)\-":] {2,}[\w.?!,\(\)\-":]'

I mean, Vale shouldn't be scanning code blocks, but @eread and @marcel.amirault and I have all encountered in the past that rules with anything regex-like can be overly grabby and tough to disable. Is that what's happening here? Is it possible that the lack of scope is letting this rule work like a raw-scoped rule, and ingest code blocks?

I can't get this rule to fail reliably with my own edits, but you can reproduce it locally by reversing my changes to Max's merge request:

1. git fetch origin
2. git checkout -b 'mw/o11y/django-tutorial' 'origin/mw/o11y/django-tutorial' from !159440
3. open doc/tutorials/observability/observability_django_tutorial.md
4. Remove the rule-disabling codes on line 24 and the end of the file, and resave the file
5. line 110-ish should fail

Setting any of these scopes in SentenceSpacing.yml removes the error:

• scope: text.html (the broadest scope I can find)
• scope: paragraph (narrower)
• scope: sentence (probably too narrow but I'm unsure how to test)

I think we probably want to keep the scope of this rule as broad as possible without triggering the problem, but I need more eyes.

Related issues

Related to Draft: Add Django tutorial for observability to... (!159440) where I spotted the problem.

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