Remove the UTF-8 fallback, when TextDecoder is missing, from the Content-Disposition parser

Given that `TextDecoder` is now supported by all modern browsers/environments, please see https://developer.mozilla.org/en-US/docs/Web/API/TextDecoder#browser_compatibility, there's no longer any good reason to keep a UTF-8 fallback in the Content-Disposition parser.

src/display/content_disposition.js

@@ -19,7 +19,6 @@ import { stringToBytes } from "../shared/util.js";
 // https://github.com/Rob--W/open-in-browser/blob/7e2e35a38b8b4e981b11da7b2f01df0149049e92/extension/content-disposition.js
 // with the following changes:
 // - Modified to conform to PDF.js's coding style.
-// - Support UTF-8 decoding when TextDecoder is unsupported.
 // - Move return to the end of the function to prevent Babel from dropping the
 //   function declarations.
 
@@ -92,14 +91,6 @@ function getFilenameFromContentDispositionHeader(contentDisposition) {
         needsEncodingFixup = false;
       } catch (e) {
         // TextDecoder constructor threw - unrecognized encoding.
-        // Or TextDecoder API is not available (in IE / Edge).
-        if (/^utf-?8$/i.test(encoding)) {
-          // UTF-8 is commonly used, try to support it in another way:
-          try {
-            value = decodeURIComponent(escape(value));
-            needsEncodingFixup = false;
-          } catch (err) {}
-        }
       }
     }
     return value;