Fix docs example for migrate create

[MasterOdin]

This reverts commit 1187a5b.

From #2263 (comment):

When you provide a class name, then we hit this line to get the filename:

phinx/src/Phinx/Console/Command/Create.php

Line 183 in 5c28445

$fileName = Util::mapClassNameToFileName($className);

which per the comment:

phinx/src/Phinx/Util/Util.php

Lines 103 to 105 in 5c28445

	* Turn migration names like 'CreateUserTable' into file names like
	* '12345678901234_create_user_table.php' or 'LimitResourceNamesTo30Chars' into
	* '12345678901234_limit_resource_names_to_30_chars.php'.

The tests for this function also back up the behavior here:

phinx/tests/Phinx/Util/UtilTest.php

Lines 71 to 86 in 5c28445

	public function providerMapClassNameToFileName(): array
	{
	return [
	['CamelCase87afterSomeBooze', '/^\d{14}_camel_case_87after_some_booze\.php$/'],
	['CreateUserTable', '/^\d{14}_create_user_table\.php$/'],
	['LimitResourceNamesTo30Chars', '/^\d{14}_limit_resource_names_to_30_chars\.php$/'],
	];
	}
	/**
	* @dataProvider providerMapClassNameToFileName
	*/
	public function testMapClassNameToFileName(string $name, string $pattern): void
	{
	$this->assertMatchesRegularExpression($pattern, Util::mapClassNameToFileName($name));
	}

I think the capitalization that the docs was changed to might be a cakephp/migrations thing and not what phinx itself does?

[dereuromark]

Interesting. Might be then yeah
While it makes sense to have the name closer to the class name I guess this is a breaking change.
Feel free to merge

[MasterOdin]

We could certainly make this a feature flag if it's desired behavior, though at that point, might be better to just go for filenames that adhere to PSR-4.