[TASK] Use utf8 as default charset for SQLite and PostgreSQL

Literally, PostgresSQL and SQLite are smart enough to map
`utf-8` correctly to their internal charset `utf8`, which
means that the default would be okay.

Recently added to the testing-framework, this has been
handled before by TYPO3 core using `utf8`, it's changed
to streamline towards the same writing throughout TYPO3.

Releases: main, 8

Author: sbuerk

Classes/Core/Functional/FunctionalTestCase.php

@@ -367,7 +367,7 @@ protected function setUp(): void
                 }
                 // Postgres/SQLite requires to use `utf-8` as charset and does not support `utf8mb4`.
                 if (($localConfiguration['DB']['Connections']['Default']['charset'] ?? '') === '') {
-                    $localConfiguration['DB']['Connections']['Default']['charset'] = 'utf-8';
+                    $localConfiguration['DB']['Connections']['Default']['charset'] = 'utf8';
                 }
             } else {
                 // sqlite dbs of all tests are stored in a dir parallel to instance roots. Allows defining this path as tmpfs.