Fixed test failures on PHP 7.4

The failures are caused by the changes in PHP according to https://wiki.php.net/rfc/notice-for-non-valid-array-container.

tests/Doctrine/Tests/DBAL/Driver/OCI8/OCI8StatementTest.php

@@ -59,6 +59,11 @@ public function testExecute(array $params) : void
  $this->equalTo($params[2])
  );
 
+ // the return value is irrelevant to the test
+ // but it has to be compatible with the method signature
+ $statement->method('errorInfo')
+ ->willReturn(false);
+
  // can't pass to constructor since we don't have a real database handle,
  // but execute must check the connection for the executeMode
  $conn = $this->getMockBuilder(OCI8Connection::class)

tests/Doctrine/Tests/DBAL/Sharding/PoolingShardManagerTest.php

@@ -47,6 +47,10 @@ public function testSelectGlobal() : void
  {
  $conn = $this->createConnectionMock();
  $conn->expects($this->once())->method('connect')->with($this->equalTo(0));
+ $conn->method('getParams')
+ ->willReturn([
+ 'shardChoser' => $this->createMock(ShardChoser::class),
+ ]);
 
  $shardManager = new PoolingShardManager($conn);
  $shardManager->selectGlobal();