Update test Issue874: Now finds more text on page 1

With the fix for including associated streams, this test now finds more text on the first page. I've verified using Aspose.PDF and by viewing the ErcotFacts.pdf file being tested that yes, it was indeed missing part of the text before.

src/UglyToad.PdfPig.Tests/Integration/GithubIssuesTests.cs

@@ -475,7 +475,7 @@
             using (var document = PdfDocument.Open(doc, new ParsingOptions() { UseLenientParsing = true, SkipMissingFonts = true }))
             {
                 var page1 = document.GetPage(1);
-                Assert.Equal(1788, page1.Letters.Count);
+                Assert.Equal(1939, page1.Letters.Count);
 
                 var page2 = document.GetPage(2);
                 Assert.Equal(2430, page2.Letters.Count);