Update README

@@ -50,7 +50,7 @@ for documentation.
 6. For Windows and Linux, you can force the pdfium version and architecture
    on your main `CMakeLists.txt` with:
 
-   ```dart
+   ```python
    set(PDFIUM_VERSION "4929" CACHE STRING "" FORCE)
    set(PDFIUM_ARCH "x64" CACHE STRING "" FORCE)
    ```

@@ -54,7 +54,6 @@ void buildFile(String src, String dest, bool flutter) {
   st.writeln('import \'dart:typed_data\';');
   if (flutter) {
     st.writeln('import \'package:flutter/services.dart\' show rootBundle;');
-    st.writeln('import \'package:flutter/widgets.dart\' show AssetImage;');
     st.writeln('import \'package:path_provider/path_provider.dart\';');
   }
   st.writeln('import \'package:printing/printing.dart\';');