Tests: Explicitly set cursor position

[hroncok]

Since we updated QScintilla 2.13 -> 2.14 in Fedora 41+, we see this test failure:

_____________ test_EditorPane_toggle_comments_handle_crlf_newline ______________
    def test_EditorPane_toggle_comments_handle_crlf_newline():
        """
        Check that stray "\r\n" line endings don't lead to deleting the first
        character of the following line.
        """
        ep = mu.interface.editor.EditorPane(None, "test\r\nline 2\n")
        ep.hasSelectedText = mock.MagicMock(return_value=False)
        ep.toggle_comments()
>       assert ep.text() == "# test\nline 2\n"
E       AssertionError: assert 'test\r\nline 2\n' == '# test\nline 2\n'
E
E         - # test
E         ? --
E         + test
E         ?     +
E           line 2
tests/interface/test_editor.py:940: AssertionError

I've added some debugging prints and realized that getCursorPosition() returns 2, 0 in this test, while is assumes the cursor is on line 0.

By explicitly calling setCursorPosition() we fix the test and we make it more clear to the reader.