[file_packager] Remove unused errback fetchRemovePackage. NFC

This argument has been used since 3839dd4.

Even when this function was first add in 74f3242 the errback
callback was only used for the IDB failures, not the fetch failures.
Fetch failure were left to propagate to the global error handlers.

This is small cleanup in advance of emscripten-core#24893.

Author: sbc100

tools/file_packager.py

@@ -964,7 +964,7 @@ def generate_js(data_target, data_files, metadata):
         }'''.strip()
 
     ret += '''
-      function fetchRemotePackage(packageName, packageSize, callback, errback) {
+      function fetchRemotePackage(packageName, packageSize, callback) {
         %(node_support_code)s
         Module['dataFileDownloads'] ??= {};
         fetch(packageName)
@@ -1044,7 +1044,7 @@ def generate_js(data_target, data_files, metadata):
         function preloadFallback(error) {
           console.error(error);
           console.error('falling back to default preload behavior');
-          fetchRemotePackage(REMOTE_PACKAGE_NAME, REMOTE_PACKAGE_SIZE, processPackageData, handleError);
+          fetchRemotePackage(REMOTE_PACKAGE_NAME, REMOTE_PACKAGE_SIZE, processPackageData);
         };
 
         openDatabase()
@@ -1063,8 +1063,7 @@ def generate_js(data_target, data_files, metadata):
                         console.error(error);
                         processPackageData(packageData);
                       });
-                  }
-                , preloadFallback);
+                  });
               }
             })
           }).catch(preloadFallback);
@@ -1086,7 +1085,7 @@ def generate_js(data_target, data_files, metadata):
         } else {
           fetched = data;
         }
-      }, handleError);\n'''
+      });\n'''
 
       code += '''
       Module['preloadResults'][PACKAGE_NAME] = {fromCache: false};