Stop using the PRODUCTION build-target in the JavaScript code

This *special* build-target is very old, and was introduced with the first pre-processor that only uses comments to enable/disable code.
When the new pre-processor was added `PRODUCTION` effectively became redundant, at least in JavaScript code, since `typeof PDFJSDev === "undefined"` checks now do the same thing.

This patch proposes that we remove `PRODUCTION` from the JavaScript code, since that simplifies the conditions and thus improves readability in many cases.
*Please note:* There's not, nor has there ever been, any gulp-task that set `PRODUCTION = false` during building.

web/preferences.js

@@ -22,7 +22,7 @@ import { AppOptions, OptionKind } from "./app_options.js";
  */
 class BasePreferences {
   #defaults = Object.freeze(
-    typeof PDFJSDev === "undefined" || !PDFJSDev.test("PRODUCTION")
+    typeof PDFJSDev === "undefined"
       ? AppOptions.getAll(OptionKind.PREFERENCE)
       : PDFJSDev.eval("DEFAULT_PREFERENCES")
   );