MDL-67673 phpunit: Remove expectedException annotations

While this is not strictly required, because removal will
happen in PHPUnit 9.0, we are already getting rid of all
uses in core.

From release notes:https://phpunit.de/announcements/phpunit-8.html

The annotations `@expectedException`, `@expectedExceptionCode`,
`@expectedExceptionMessage`, and `@expectedExceptionMessageRegExp`
are now deprecated.
Using these annotations will trigger a deprecation warning
in PHPUnit 8 and in PHPUnit 9 these annotations will be removed.

Also, all uses of expectExceptionMessageRegExp() has been moved
to expectExceptionMessageMatches(). See https://github.com/sebastianbergmann/phpunit/issues/3957

TODO: Various weirdness found while doing the changes with these tests:
- vendor/bin/phpunit lib/tests/exporter_test.php (created MDL-69700)
- vendor/bin/phpunit competency/tests/external_test.php (same issue than prev one)
- vendor/bin/phpunit question/engine/tests/questionengine_test.php (created MDL-69624)
- vendor/bin/phpunit lib/tests/event_test.php (created MDL-69688)

lib/tests/update_code_manager_test.php

@@ -111,14 +111,12 @@ class core_update_code_manager_testcase extends advanced_testcase {
         $files = $codeman->unzip_plugin_file($zipfilepath, $targetdir, 'bar');
     }
 
-    /**
-     * @expectedException moodle_exception
-     */
     public function test_unzip_plugin_file_multidir() {
         $codeman = new \core\update\testable_code_manager();
         $zipfilepath = __DIR__.'/fixtures/update_validator/zips/multidir.zip';
         $targetdir = make_request_directory();
         // Attempting to rename the root folder if there are multiple ones should lead to exception.
+        $this->expectException(moodle_exception::class);
         $files = $codeman->unzip_plugin_file($zipfilepath, $targetdir, 'foo');
     }