Remove DateAxisItem custom implementation

[xoriole]

DateAxisItem is now merged in pyqtgraph so we don't need the custom implementation anymore.

[xoriole]

Test on Windows 64-bit failed, not related to this PR

Error Message

AttributeError: 'NoneType' object has no attribute 'split'

Stacktrace

self = <test_triblertunnel_community.TestTriblerTunnelCommunity testMethod=test_perform_http_request_multipart>

    async def test_perform_http_request_multipart(self):
        """
        Test whether getting a large HTTP response works
        """
        self.add_node_to_experiment(self.create_node())
        self.nodes[1].overlay.settings.peer_flags.add(PEER_FLAG_EXIT_HTTP)
        await self.introduce_nodes()
    
        http_port = TestTriblerTunnelCommunity.get_free_port()
        http_tracker = HTTPTracker(http_port)
        http_tracker.tracker_info.add_info_about_infohash('0', 0, 0)
        http_tracker.tracker_info.infohashes['0']['downloaded'] = os.urandom(10000)
        await http_tracker.start()
        response = await self.nodes[0].overlay.perform_http_request(('127.0.0.1', http_tracker.port),
                                                                    b'GET /scrape?info_hash=0 HTTP/1.1\r\n\r\n')
    
>       self.assertEqual(response.split(b'\r\n')[0], b'HTTP/1.1 200 OK')
E       AttributeError: 'NoneType' object has no attribute 'split'

src\tribler-core\tribler_core\modules\tunnel\tests\test_triblertunnel_community.py:593: AttributeError

[xoriole]

retest this please

[devos50]

@xoriole I couldn't find an existing issue for this stack trace. Let's create one?

[sonarqubecloud]

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