[file_packager] Remove unused errback fetchRemovePackage. NFC (#24904)

This argument has been used since 3839dd4.

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

The exception here was that when node support was added in #11785 it, I
believe incorrectly used errback to handle file read errors (doesn't
match the web version that does *not* handle fetch error using errback).

I'm not claiming this is correct/best behaviour, this is simply an NFC
to cleanup an already-unused argument.

This is small cleanup in advance of #24893.

Author: sbc100

tools/file_packager.py

@@ -953,18 +953,12 @@ def generate_js(data_target, data_files, metadata):
     if options.support_node:
       node_support_code = '''
         if (isNode) {
-          require('fs').readFile(packageName, (err, contents) => {
-            if (err) {
-              errback(err);
-            } else {
-              callback(contents.buffer);
-            }
-          });
+          require('fs/promises').readFile(packageName).then((contents) => callback(contents.buffer));
           return;
         }'''.strip()
 
     ret += '''
-      function fetchRemotePackage(packageName, packageSize, callback, errback) {
+      function fetchRemotePackage(packageName, packageSize, callback) {
         %(node_support_code)s
         Module['dataFileDownloads'] ??= {};
         fetch(packageName)
@@ -1040,7 +1034,7 @@ 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()
@@ -1059,8 +1053,7 @@ def generate_js(data_target, data_files, metadata):
                         console.error(error);
                         processPackageData(packageData);
                       });
-                  }
-                , preloadFallback);
+                  });
               }
             })
           }).catch(preloadFallback);
@@ -1082,7 +1075,7 @@ def generate_js(data_target, data_files, metadata):
         } else {
           fetched = data;
         }
-      }, handleError);\n'''
+      });\n'''
 
       code += '''
       Module['preloadResults'][PACKAGE_NAME] = {fromCache: false};