build: reach lopdf and encoding_rs through printpdf and the codec

#1418 added both as direct dependencies although each was already in the
tree: printpdf's to_lopdf_doc returns the lopdf document whose compress
and save_to are plain methods, and the codec's encoding_from_code_page
hands back the Big5 / GBK / Shift_JIS / EUC-KR encodings by their DXF
code-page names. Cargo.toml keeps its dependency list.

Co-Authored-By: Claude Fable 5.1 <[email protected]>

Cargo.lock

@@ -18,7 +18,6 @@ dependencies = [
  "console_error_panic_hook",
  "cosmic-text 0.15.0",
  "dwg-thumbnailer",
- "encoding_rs",
  "env_logger",
  "flate2",
  "fluent-syntax",
@@ -38,7 +37,6 @@ dependencies = [
  "js-sys",
  "libloading",
  "log",
- "lopdf",
  "lyon_tessellation",
  "meshopt",
  "naga 27.0.3",