ci: fix call to ldoc (#14207)

Since luarocks >= 3.12.0 is broken, and does not honor `wrap_bin_scripts
= false` anymore, just call ldoc directly so it works even if a wrapper
script is used.

.ci/after_success_docs_translation.sh

@@ -24,7 +24,7 @@ git clone git@github.com:koreader/doc.git koreader_doc
 
 # push doc update
 pushd doc && {
-    luajit "$(command -v ldoc)" .
+    ldoc .
     if [ ! -d html ]; then
         echo "Failed to generate documents..."
         exit 1