Fix broken 29fd612

The 29fd612 commit accidentally only changed the corresponding comment,
but didn't actually change the _code_. Oops.

src/language.cpp

@@ -501,7 +501,7 @@ Language Language::TryDetectFromText(const char *buffer, size_t len, Language pr
 
     auto lang = CLD2::ExtDetectLanguageSummary(
                         buffer, (int)len,
-                        /*is_plain_text=*/false, // any embedded HTML markup should be insignificant
+                        /*is_plain_text=*/true, // any embedded HTML markup should be insignificant
                         &hints,
                         /*flags=*/0,
                         language3, percent3, normalized_score3,