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.

Author: morozov

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();