[Sets] Drop the PHPUnit 12.0, 12.5 and 13.0 triggered sets covered by composer-based

[TomasVotruba]

Same cleanup as rectorphp/rector-symfony#1010, but PHPUnit turns out to be a much smaller case — most per-version sets are not covered by composer-based.php yet, so only three go.

Checked all 11 triggered sets rule by rule against config/sets/composer-based.php:

set	covered	why
12.0	yes	RemoveOverrideFinalConstructTestCaseRector (>=12.0.3), plus the mock-to-stub and composer-based sets it imports — all 10 mock-to-stub rules are in composer-based
12.5	yes	the three AllowMockObjects* rules (>=12.5.2)
13.0	yes	the expectExceptionMessage() → expectExceptionMessageIsOrContains() rename (>=13.2)
4.0	no	the staticExpects() → expects() rename is not in composer-based
5.0–11.0	no	5 to 7 rules each still only in their version set

-            new ComposerTriggeredSet(
-                SetGroup::PHPUNIT,
-                'phpunit/phpunit',
-                '12.5',
-                __DIR__ . '/../../../config/sets/phpunit125.php'
-            ),

The version bond is also more accurate than the set trigger it replaces. The set fired on ^13.0, while the method it renames to only exists from 13.2:

// composer-based.php
$rectorConfig->ruleWithConfigurationComposerVersionBound(RenameMethodRector::class, [
    new MethodCallRename(
        'PHPUnit\Framework\TestCase',
        'expectExceptionMessage',
        'expectExceptionMessageIsOrContains'
    ),
], 'phpunit/phpunit', '>=13.2');

Same for 12.0 vs 12.0.3 and 12.5 vs 12.5.2. A project on 13.0 or 13.1 no longer gets a rename to a method it does not have.

PHPUnitSetProvider stays — it still carries the 8 uncovered per-version sets, the composer-based trigger, and the Code Quality and PHPUnit Attributes sets. The three set files stay reachable through PHPUnitSetList::PHPUNIT_120, PHPUNIT_125 and PHPUNIT_130.

Green locally: 652 tests, PHPStan and ECS clean.