gh-156233: Fix grammar in MRO documentation

[aryansk]

Fixes #156233

Problem

Doc/howto/mro.rst contains a grammar typo:

Then repeat the operation until all the class are removed or it is impossible to find good heads.

Singular "class" disagrees with plural verb "are". The sentence describes removing multiple classes during MRO merge, so plural "classes" is correct.

Issue: #156233
Source: Doc/howto/mro.rst:192 (Doc/howto/mro.html#python-2-3-mro)

Change

• Fix Doc/howto/mro.rst:192 from all the class are removed → all the classes are removed
• Keep unrelated cleanup out of this PR

Why this approach

Minimal one-line docs fix matching the issue's suggested correction. No code or behavior change.

Testing

command: git diff --check
result: clean

command: grep -n "all the class" Doc/howto/mro.rst
result: no matches (fixed)

command: grep -n "all the classes are removed" Doc/howto/mro.rst
result: 192:  the operation until all the classes are removed or it is impossible to

Doc build: Doc/howto/mro.rst renders as before with corrected grammar; no functional tests required for docs-only change.

Documentation and release impact

• User-facing documentation updated
• Changelog/release note needed: docs fix, no NEWS blurb required per CPython docs-only convention (trivial typo)
• Migration or compatibility note needed
• No documentation impact

Review notes

• Known limitations: none
• Follow-up issue, if any: none
• Security/licensing considerations: none

• Issue: A tiny grammar issue in the Python MRO documentation: "all the class" should be "all the classes" #156233

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Documentation build overview

📚 cpython-previews | 🛠️ Build #34207577 | 📁 Comparing 6b7f5b3 against main (ee1da7e)

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1 file changed

± howto/mro.html