remove error-demo from make; clean up comment

Makefile

@@ -17,8 +17,7 @@ makefiles = \
   misc/upstart/local.mk \
   doc/manual/local.mk \
   tests/local.mk \
-  tests/plugins/local.mk \
-  src/error-demo/local.mk
+  tests/plugins/local.mk 
 
 -include Makefile.config
 

src/libexpr/parser.y

@@ -663,7 +663,6 @@ Expr * EvalState::parseExprFromString(std::string_view s, const Path & basePath)
 Expr * EvalState::parseStdin()
 {
     //Activity act(*logger, lvlTalkative, format("parsing standard input"));
-    // return parseExprFromString(foStdin, drainFD(0), absPath("."));
     return parse(drainFD(0).data(), foStdin, "", absPath("."), staticBaseEnv);
 }